diff --git a/cmd_geo.go b/cmd_geo.go
index 6702e96..97f74c3 100644
--- a/cmd_geo.go
+++ b/cmd_geo.go
@@ -40,7 +40,7 @@ func (m *Miniredis) cmdGeoadd(c *server.Peer, cmd string, args []string) {
 	withTx(m, c, func(c *server.Peer, ctx *connCtx) {
 		db := m.db(ctx.selectedDB)
 
-		if db.exists(key) && db.t(key) != "zset" {
+		if db.exists(key) && db.t(key) != keyTypeSortedSet {
 			c.WriteError(ErrWrongType.Error())
 			return
 		}
@@ -103,7 +103,7 @@ func (m *Miniredis) cmdGeodist(c *server.Peer, cmd string, args []string) {
 			c.WriteNull()
 			return
 		}
-		if db.t(key) != "zset" {
+		if db.t(key) != keyTypeSortedSet {
 			c.WriteError(ErrWrongType.Error())
 			return
 		}
@@ -157,7 +157,7 @@ func (m *Miniredis) cmdGeopos(c *server.Peer, cmd string, args []string) {
 	withTx(m, c, func(c *server.Peer, ctx *connCtx) {
 		db := m.db(ctx.selectedDB)
 
-		if db.exists(key) && db.t(key) != "zset" {
+		if db.exists(key) && db.t(key) != keyTypeSortedSet {
 			c.WriteError(ErrWrongType.Error())
 			return
 		}
@@ -495,7 +495,7 @@ func (m *Miniredis) cmdGeoradiusbymember(c *server.Peer, cmd string, args []stri
 			return
 		}
 
-		if db.t(opts.key) != "zset" {
+		if db.t(opts.key) != keyTypeSortedSet {
 			c.WriteError(ErrWrongType.Error())
 			return
 		}
diff --git a/cmd_hash.go b/cmd_hash.go
index 2c45630..5533295 100644
--- a/cmd_hash.go
+++ b/cmd_hash.go
@@ -54,7 +54,7 @@ func (m *Miniredis) cmdHset(c *server.Peer, cmd string, args []string) {
 			return
 		}
 
-		if t, ok := db.keys[key]; ok && t != "hash" {
+		if t, ok := db.keys[key]; ok && t != keyTypeHash {
 			c.WriteError(msgWrongType)
 			return
 		}
@@ -91,14 +91,14 @@ func (m *Miniredis) cmdHsetnx(c *server.Peer, cmd string, args []string) {
 	withTx(m, c, func(c *server.Peer, ctx *connCtx) {
 		db := m.db(ctx.selectedDB)
 
-		if t, ok := db.keys[opts.key]; ok && t != "hash" {
+		if t, ok := db.keys[opts.key]; ok && t != keyTypeHash {
 			c.WriteError(msgWrongType)
 			return
 		}
 
 		if _, ok := db.hashKeys[opts.key]; !ok {
 			db.hashKeys[opts.key] = map[string]string{}
-			db.keys[opts.key] = "hash"
+			db.keys[opts.key] = keyTypeHash
 		}
 		_, ok := db.hashKeys[opts.key][opts.field]
 		if ok {
@@ -135,7 +135,7 @@ func (m *Miniredis) cmdHmset(c *server.Peer, cmd string, args []string) {
 	withTx(m, c, func(c *server.Peer, ctx *connCtx) {
 		db := m.db(ctx.selectedDB)
 
-		if t, ok := db.keys[key]; ok && t != "hash" {
+		if t, ok := db.keys[key]; ok && t != keyTypeHash {
 			c.WriteError(msgWrongType)
 			return
 		}
@@ -173,7 +173,7 @@ func (m *Miniredis) cmdHget(c *server.Peer, cmd string, args []string) {
 			c.WriteNull()
 			return
 		}
-		if t != "hash" {
+		if t != keyTypeHash {
 			c.WriteError(msgWrongType)
 			return
 		}
@@ -217,7 +217,7 @@ func (m *Miniredis) cmdHdel(c *server.Peer, cmd string, args []string) {
 			c.WriteInt(0)
 			return
 		}
-		if t != "hash" {
+		if t != keyTypeHash {
 			c.WriteError(msgWrongType)
 			return
 		}
@@ -270,7 +270,7 @@ func (m *Miniredis) cmdHexists(c *server.Peer, cmd string, args []string) {
 			c.WriteInt(0)
 			return
 		}
-		if t != "hash" {
+		if t != keyTypeHash {
 			c.WriteError(msgWrongType)
 			return
 		}
@@ -307,7 +307,7 @@ func (m *Miniredis) cmdHgetall(c *server.Peer, cmd string, args []string) {
 			c.WriteMapLen(0)
 			return
 		}
-		if t != "hash" {
+		if t != keyTypeHash {
 			c.WriteError(msgWrongType)
 			return
 		}
@@ -343,7 +343,7 @@ func (m *Miniredis) cmdHkeys(c *server.Peer, cmd string, args []string) {
 			c.WriteLen(0)
 			return
 		}
-		if db.t(key) != "hash" {
+		if db.t(key) != keyTypeHash {
 			c.WriteError(msgWrongType)
 			return
 		}
@@ -380,7 +380,7 @@ func (m *Miniredis) cmdHstrlen(c *server.Peer, cmd string, args []string) {
 			c.WriteInt(0)
 			return
 		}
-		if t != "hash" {
+		if t != keyTypeHash {
 			c.WriteError(msgWrongType)
 			return
 		}
@@ -414,7 +414,7 @@ func (m *Miniredis) cmdHvals(c *server.Peer, cmd string, args []string) {
 			c.WriteLen(0)
 			return
 		}
-		if t != "hash" {
+		if t != keyTypeHash {
 			c.WriteError(msgWrongType)
 			return
 		}
@@ -451,7 +451,7 @@ func (m *Miniredis) cmdHlen(c *server.Peer, cmd string, args []string) {
 			c.WriteInt(0)
 			return
 		}
-		if t != "hash" {
+		if t != keyTypeHash {
 			c.WriteError(msgWrongType)
 			return
 		}
@@ -479,7 +479,7 @@ func (m *Miniredis) cmdHmget(c *server.Peer, cmd string, args []string) {
 	withTx(m, c, func(c *server.Peer, ctx *connCtx) {
 		db := m.db(ctx.selectedDB)
 
-		if t, ok := db.keys[key]; ok && t != "hash" {
+		if t, ok := db.keys[key]; ok && t != keyTypeHash {
 			c.WriteError(msgWrongType)
 			return
 		}
@@ -530,7 +530,7 @@ func (m *Miniredis) cmdHincrby(c *server.Peer, cmd string, args []string) {
 	withTx(m, c, func(c *server.Peer, ctx *connCtx) {
 		db := m.db(ctx.selectedDB)
 
-		if t, ok := db.keys[opts.key]; ok && t != "hash" {
+		if t, ok := db.keys[opts.key]; ok && t != keyTypeHash {
 			c.WriteError(msgWrongType)
 			return
 		}
@@ -577,7 +577,7 @@ func (m *Miniredis) cmdHincrbyfloat(c *server.Peer, cmd string, args []string) {
 	withTx(m, c, func(c *server.Peer, ctx *connCtx) {
 		db := m.db(ctx.selectedDB)
 
-		if t, ok := db.keys[opts.key]; ok && t != "hash" {
+		if t, ok := db.keys[opts.key]; ok && t != keyTypeHash {
 			c.WriteError(msgWrongType)
 			return
 		}
@@ -662,7 +662,7 @@ func (m *Miniredis) cmdHscan(c *server.Peer, cmd string, args []string) {
 			c.WriteLen(0)    // no elements
 			return
 		}
-		if db.exists(opts.key) && db.t(opts.key) != "hash" {
+		if db.exists(opts.key) && db.t(opts.key) != keyTypeHash {
 			c.WriteError(ErrWrongType.Error())
 			return
 		}
diff --git a/cmd_hll.go b/cmd_hll.go
index a7b4836..ffb4d6f 100644
--- a/cmd_hll.go
+++ b/cmd_hll.go
@@ -28,7 +28,7 @@ func (m *Miniredis) cmdPfadd(c *server.Peer, cmd string, args []string) {
 	withTx(m, c, func(c *server.Peer, ctx *connCtx) {
 		db := m.db(ctx.selectedDB)
 
-		if db.exists(key) && db.t(key) != "hll" {
+		if db.exists(key) && db.t(key) != keyTypeHll {
 			c.WriteError(ErrNotValidHllValue.Error())
 			return
 		}
diff --git a/cmd_list.go b/cmd_list.go
index d224275..5819945 100644
--- a/cmd_list.go
+++ b/cmd_list.go
@@ -84,7 +84,7 @@ func (m *Miniredis) cmdBXpop(c *server.Peer, cmd string, args []string, lr leftr
 				if !db.exists(key) {
 					continue
 				}
-				if db.t(key) != "list" {
+				if db.t(key) != keyTypeList {
 					c.WriteError(msgWrongType)
 					return true
 				}
@@ -145,7 +145,7 @@ func (m *Miniredis) cmdLindex(c *server.Peer, cmd string, args []string) {
 			c.WriteNull()
 			return
 		}
-		if t != "list" {
+		if t != keyTypeList {
 			c.WriteError(msgWrongType)
 			return
 		}
@@ -239,7 +239,7 @@ func (m *Miniredis) cmdLpos(c *server.Peer, cmd string, args []string) {
 			c.WriteNull()
 			return
 		}
-		if t != "list" {
+		if t != keyTypeList {
 			c.WriteError(msgWrongType)
 			return
 		}
@@ -347,7 +347,7 @@ func (m *Miniredis) cmdLinsert(c *server.Peer, cmd string, args []string) {
 			c.WriteInt(0)
 			return
 		}
-		if t != "list" {
+		if t != keyTypeList {
 			c.WriteError(msgWrongType)
 			return
 		}
@@ -401,7 +401,7 @@ func (m *Miniredis) cmdLlen(c *server.Peer, cmd string, args []string) {
 			c.WriteInt(0)
 			return
 		}
-		if t != "list" {
+		if t != keyTypeList {
 			c.WriteError(msgWrongType)
 			return
 		}
@@ -471,7 +471,7 @@ func (m *Miniredis) cmdXpop(c *server.Peer, cmd string, args []string, lr leftri
 			c.WriteNull()
 			return
 		}
-		if db.t(opts.key) != "list" {
+		if db.t(opts.key) != keyTypeList {
 			c.WriteError(msgWrongType)
 			return
 		}
@@ -530,7 +530,7 @@ func (m *Miniredis) cmdXpush(c *server.Peer, cmd string, args []string, lr leftr
 	withTx(m, c, func(c *server.Peer, ctx *connCtx) {
 		db := m.db(ctx.selectedDB)
 
-		if db.exists(key) && db.t(key) != "list" {
+		if db.exists(key) && db.t(key) != keyTypeList {
 			c.WriteError(msgWrongType)
 			return
 		}
@@ -580,7 +580,7 @@ func (m *Miniredis) cmdXpushx(c *server.Peer, cmd string, args []string, lr left
 			c.WriteInt(0)
 			return
 		}
-		if db.t(key) != "list" {
+		if db.t(key) != keyTypeList {
 			c.WriteError(msgWrongType)
 			return
 		}
@@ -629,7 +629,7 @@ func (m *Miniredis) cmdLrange(c *server.Peer, cmd string, args []string) {
 	withTx(m, c, func(c *server.Peer, ctx *connCtx) {
 		db := m.db(ctx.selectedDB)
 
-		if t, ok := db.keys[opts.key]; ok && t != "list" {
+		if t, ok := db.keys[opts.key]; ok && t != keyTypeList {
 			c.WriteError(msgWrongType)
 			return
 		}
@@ -680,7 +680,7 @@ func (m *Miniredis) cmdLrem(c *server.Peer, cmd string, args []string) {
 			c.WriteInt(0)
 			return
 		}
-		if db.t(opts.key) != "list" {
+		if db.t(opts.key) != keyTypeList {
 			c.WriteError(msgWrongType)
 			return
 		}
@@ -754,7 +754,7 @@ func (m *Miniredis) cmdLset(c *server.Peer, cmd string, args []string) {
 			c.WriteError(msgKeyNotFound)
 			return
 		}
-		if db.t(opts.key) != "list" {
+		if db.t(opts.key) != keyTypeList {
 			c.WriteError(msgWrongType)
 			return
 		}
@@ -811,7 +811,7 @@ func (m *Miniredis) cmdLtrim(c *server.Peer, cmd string, args []string) {
 			c.WriteOK()
 			return
 		}
-		if t != "list" {
+		if t != keyTypeList {
 			c.WriteError(msgWrongType)
 			return
 		}
@@ -852,7 +852,7 @@ func (m *Miniredis) cmdRpoplpush(c *server.Peer, cmd string, args []string) {
 			c.WriteNull()
 			return
 		}
-		if db.t(src) != "list" || (db.exists(dst) && db.t(dst) != "list") {
+		if db.t(src) != keyTypeList || (db.exists(dst) && db.t(dst) != keyTypeList) {
 			c.WriteError(msgWrongType)
 			return
 		}
@@ -897,7 +897,7 @@ func (m *Miniredis) cmdBrpoplpush(c *server.Peer, cmd string, args []string) {
 			if !db.exists(opts.src) {
 				return false
 			}
-			if db.t(opts.src) != "list" || (db.exists(opts.dst) && db.t(opts.dst) != "list") {
+			if db.t(opts.src) != keyTypeList || (db.exists(opts.dst) && db.t(opts.dst) != keyTypeList) {
 				c.WriteError(msgWrongType)
 				return true
 			}
@@ -949,7 +949,7 @@ func (m *Miniredis) cmdLmove(c *server.Peer, cmd string, args []string) {
 			c.WriteNull()
 			return
 		}
-		if db.t(opts.src) != "list" || (db.exists(opts.dst) && db.t(opts.dst) != "list") {
+		if db.t(opts.src) != keyTypeList || (db.exists(opts.dst) && db.t(opts.dst) != keyTypeList) {
 			c.WriteError(msgWrongType)
 			return
 		}
@@ -1017,7 +1017,7 @@ func (m *Miniredis) cmdBlmove(c *server.Peer, cmd string, args []string) {
 			if !db.exists(opts.src) {
 				return false
 			}
-			if db.t(opts.src) != "list" || (db.exists(opts.dst) && db.t(opts.dst) != "list") {
+			if db.t(opts.src) != keyTypeList || (db.exists(opts.dst) && db.t(opts.dst) != keyTypeList) {
 				c.WriteError(msgWrongType)
 				return true
 			}
diff --git a/cmd_server.go b/cmd_server.go
index 6a41a43..5fe55dd 100644
--- a/cmd_server.go
+++ b/cmd_server.go
@@ -57,19 +57,19 @@ func (m *Miniredis) cmdMemory(c *server.Peer, cmd string, args []string) {
 				ok    bool
 			)
 			switch db.keys[args[0]] {
-			case "string":
+			case keyTypeString:
 				value, ok = db.stringKeys[args[0]]
-			case "set":
+			case keyTypeSet:
 				value, ok = db.setKeys[args[0]]
-			case "hash":
+			case keyTypeHash:
 				value, ok = db.hashKeys[args[0]]
-			case "list":
+			case keyTypeList:
 				value, ok = db.listKeys[args[0]]
-			case "hll":
+			case keyTypeHll:
 				value, ok = db.hllKeys[args[0]]
-			case "zset":
+			case keyTypeSortedSet:
 				value, ok = db.sortedsetKeys[args[0]]
-			case "stream":
+			case keyTypeStream:
 				value, ok = db.streamKeys[args[0]]
 			}
 			if !ok {
diff --git a/cmd_set.go b/cmd_set.go
index abcd1ba..12e4d58 100644
--- a/cmd_set.go
+++ b/cmd_set.go
@@ -50,7 +50,7 @@ func (m *Miniredis) cmdSadd(c *server.Peer, cmd string, args []string) {
 	withTx(m, c, func(c *server.Peer, ctx *connCtx) {
 		db := m.db(ctx.selectedDB)
 
-		if db.exists(key) && db.t(key) != "set" {
+		if db.exists(key) && db.t(key) != keyTypeSet {
 			c.WriteError(ErrWrongType.Error())
 			return
 		}
diff --git a/cmd_sorted_set.go b/cmd_sorted_set.go
index bc1afc0..85bc569 100644
--- a/cmd_sorted_set.go
+++ b/cmd_sorted_set.go
@@ -142,7 +142,7 @@ outer:
 	withTx(m, c, func(c *server.Peer, ctx *connCtx) {
 		db := m.db(ctx.selectedDB)
 
-		if db.exists(opts.key) && db.t(opts.key) != "zset" {
+		if db.exists(opts.key) && db.t(opts.key) != keyTypeSortedSet {
 			c.WriteError(ErrWrongType.Error())
 			return
 		}
@@ -216,7 +216,7 @@ func (m *Miniredis) cmdZcard(c *server.Peer, cmd string, args []string) {
 			return
 		}
 
-		if db.t(key) != "zset" {
+		if db.t(key) != keyTypeSortedSet {
 			c.WriteError(ErrWrongType.Error())
 			return
 		}
@@ -272,7 +272,7 @@ func (m *Miniredis) cmdZcount(c *server.Peer, cmd string, args []string) {
 			return
 		}
 
-		if db.t(opts.key) != "zset" {
+		if db.t(opts.key) != keyTypeSortedSet {
 			c.WriteError(ErrWrongType.Error())
 			return
 		}
@@ -316,7 +316,7 @@ func (m *Miniredis) cmdZincrby(c *server.Peer, cmd string, args []string) {
 	withTx(m, c, func(c *server.Peer, ctx *connCtx) {
 		db := m.db(ctx.selectedDB)
 
-		if db.exists(opts.key) && db.t(opts.key) != "zset" {
+		if db.exists(opts.key) && db.t(opts.key) != keyTypeSortedSet {
 			c.WriteError(msgWrongType)
 			return
 		}
@@ -445,12 +445,12 @@ func (m *Miniredis) makeCmdZinter(store bool) func(c *server.Peer, cmd string, a
 
 				var set map[string]float64
 				switch db.t(key) {
-				case "set":
+				case keyTypeSet:
 					set = map[string]float64{}
 					for elem := range db.setKeys[key] {
 						set[elem] = 1.0
 					}
-				case "zset":
+				case keyTypeSortedSet:
 					set = db.sortedSet(key)
 				default:
 					c.WriteError(msgWrongType)
@@ -550,7 +550,7 @@ func (m *Miniredis) cmdZlexcount(c *server.Peer, cmd string, args []string) {
 			return
 		}
 
-		if db.t(opts.Key) != "zset" {
+		if db.t(opts.Key) != keyTypeSortedSet {
 			c.WriteError(ErrWrongType.Error())
 			return
 		}
@@ -846,7 +846,7 @@ func (m *Miniredis) makeCmdZrank(reverse bool) server.Cmd {
 				return
 			}
 
-			if db.t(key) != "zset" {
+			if db.t(key) != keyTypeSortedSet {
 				c.WriteError(ErrWrongType.Error())
 				return
 			}
@@ -900,7 +900,7 @@ func (m *Miniredis) cmdZrem(c *server.Peer, cmd string, args []string) {
 			return
 		}
 
-		if db.t(key) != "zset" {
+		if db.t(key) != keyTypeSortedSet {
 			c.WriteError(ErrWrongType.Error())
 			return
 		}
@@ -954,7 +954,7 @@ func (m *Miniredis) cmdZremrangebylex(c *server.Peer, cmd string, args []string)
 			return
 		}
 
-		if db.t(opts.Key) != "zset" {
+		if db.t(opts.Key) != keyTypeSortedSet {
 			c.WriteError(ErrWrongType.Error())
 			return
 		}
@@ -1007,7 +1007,7 @@ func (m *Miniredis) cmdZremrangebyrank(c *server.Peer, cmd string, args []string
 			return
 		}
 
-		if db.t(opts.key) != "zset" {
+		if db.t(opts.key) != keyTypeSortedSet {
 			c.WriteError(ErrWrongType.Error())
 			return
 		}
@@ -1067,7 +1067,7 @@ func (m *Miniredis) cmdZremrangebyscore(c *server.Peer, cmd string, args []strin
 			return
 		}
 
-		if db.t(opts.key) != "zset" {
+		if db.t(opts.key) != keyTypeSortedSet {
 			c.WriteError(ErrWrongType.Error())
 			return
 		}
@@ -1106,7 +1106,7 @@ func (m *Miniredis) cmdZscore(c *server.Peer, cmd string, args []string) {
 			return
 		}
 
-		if db.t(key) != "zset" {
+		if db.t(key) != keyTypeSortedSet {
 			c.WriteError(ErrWrongType.Error())
 			return
 		}
@@ -1147,7 +1147,7 @@ func (m *Miniredis) cmdZMscore(c *server.Peer, cmd string, args []string) {
 			return
 		}
 
-		if db.t(key) != "zset" {
+		if db.t(key) != keyTypeSortedSet {
 			c.WriteError(ErrWrongType.Error())
 			return
 		}
@@ -1466,12 +1466,12 @@ func executeZUnion(db *RedisDB, opts zunionOptions) (sortedSet, error) {
 
 		var set map[string]float64
 		switch db.t(key) {
-		case "set":
+		case keyTypeSet:
 			set = map[string]float64{}
 			for elem := range db.setKeys[key] {
 				set[elem] = 1.0
 			}
-		case "zset":
+		case keyTypeSortedSet:
 			set = db.sortedSet(key)
 		default:
 			return nil, errors.New(msgWrongType)
@@ -1574,7 +1574,7 @@ func (m *Miniredis) cmdZscan(c *server.Peer, cmd string, args []string) {
 
 	withTx(m, c, func(c *server.Peer, ctx *connCtx) {
 		db := m.db(ctx.selectedDB)
-		if db.exists(opts.key) && db.t(opts.key) != "zset" {
+		if db.exists(opts.key) && db.t(opts.key) != keyTypeSortedSet {
 			c.WriteError(ErrWrongType.Error())
 			return
 		}
@@ -1652,7 +1652,7 @@ func (m *Miniredis) cmdZpopmax(reverse bool) server.Cmd {
 				return
 			}
 
-			if db.t(key) != "zset" {
+			if db.t(key) != keyTypeSortedSet {
 				c.WriteError(ErrWrongType.Error())
 				return
 			}
@@ -1734,7 +1734,7 @@ func (m *Miniredis) cmdZrandmember(c *server.Peer, cmd string, args []string) {
 			return
 		}
 
-		if db.t(opts.key) != "zset" {
+		if db.t(opts.key) != keyTypeSortedSet {
 			c.WriteError(ErrWrongType.Error())
 			return
 		}
@@ -1801,7 +1801,7 @@ func runRange(m *Miniredis, c *server.Peer, cctx *connCtx, opts optsRange) {
 		return
 	}
 
-	if db.t(opts.Key) != "zset" {
+	if db.t(opts.Key) != keyTypeSortedSet {
 		c.WriteError(ErrWrongType.Error())
 		return
 	}
@@ -1864,7 +1864,7 @@ func runRangeByScore(m *Miniredis, c *server.Peer, cctx *connCtx, opts optsRange
 		return
 	}
 
-	if db.t(opts.Key) != "zset" {
+	if db.t(opts.Key) != keyTypeSortedSet {
 		c.WriteError(ErrWrongType.Error())
 		return
 	}
@@ -1951,7 +1951,7 @@ func runRangeByLex(m *Miniredis, c *server.Peer, cctx *connCtx, opts optsRangeBy
 		return
 	}
 
-	if db.t(opts.Key) != "zset" {
+	if db.t(opts.Key) != keyTypeSortedSet {
 		c.WriteError(ErrWrongType.Error())
 		return
 	}
diff --git a/cmd_stream.go b/cmd_stream.go
index 588a95f..7ce89d1 100644
--- a/cmd_stream.go
+++ b/cmd_stream.go
@@ -252,7 +252,7 @@ func (m *Miniredis) makeCmdXrange(reverse bool) server.Cmd {
 				return
 			}
 
-			if db.t(opts.key) != "stream" {
+			if db.t(opts.key) != keyTypeStream {
 				c.WriteError(ErrWrongType.Error())
 				return
 			}
diff --git a/cmd_string.go b/cmd_string.go
index b8013f2..08e6774 100644
--- a/cmd_string.go
+++ b/cmd_string.go
@@ -160,7 +160,7 @@ func (m *Miniredis) cmdSet(c *server.Peer, cmd string, args []string) {
 			}
 		}
 		if opts.get {
-			if t, ok := db.keys[opts.key]; ok && t != "string" {
+			if t, ok := db.keys[opts.key]; ok && t != keyTypeString {
 				c.WriteError(msgWrongType)
 				return
 			}
@@ -403,7 +403,7 @@ func (m *Miniredis) cmdGet(c *server.Peer, cmd string, args []string) {
 			c.WriteNull()
 			return
 		}
-		if db.t(key) != "string" {
+		if db.t(key) != keyTypeString {
 			c.WriteError(msgWrongType)
 			return
 		}
@@ -490,7 +490,7 @@ func (m *Miniredis) cmdGetex(c *server.Peer, cmd string, args []string) {
 			db.ttl[opts.key] = opts.ttl
 		}
 
-		if db.t(opts.key) != "string" {
+		if db.t(opts.key) != keyTypeString {
 			c.WriteError(msgWrongType)
 			return
 		}
@@ -518,7 +518,7 @@ func (m *Miniredis) cmdGetset(c *server.Peer, cmd string, args []string) {
 	withTx(m, c, func(c *server.Peer, ctx *connCtx) {
 		db := m.db(ctx.selectedDB)
 
-		if t, ok := db.keys[key]; ok && t != "string" {
+		if t, ok := db.keys[key]; ok && t != keyTypeString {
 			c.WriteError(msgWrongType)
 			return
 		}
@@ -560,7 +560,7 @@ func (m *Miniredis) cmdGetdel(c *server.Peer, cmd string, args []string) {
 			return
 		}
 
-		if db.t(key) != "string" {
+		if db.t(key) != keyTypeString {
 			c.WriteError(msgWrongType)
 			return
 		}
@@ -590,7 +590,7 @@ func (m *Miniredis) cmdMget(c *server.Peer, cmd string, args []string) {
 
 		c.WriteLen(len(args))
 		for _, k := range args {
-			if t, ok := db.keys[k]; !ok || t != "string" {
+			if t, ok := db.keys[k]; !ok || t != keyTypeString {
 				c.WriteNull()
 				continue
 			}
@@ -623,7 +623,7 @@ func (m *Miniredis) cmdIncr(c *server.Peer, cmd string, args []string) {
 		db := m.db(ctx.selectedDB)
 
 		key := args[0]
-		if t, ok := db.keys[key]; ok && t != "string" {
+		if t, ok := db.keys[key]; ok && t != keyTypeString {
 			c.WriteError(msgWrongType)
 			return
 		}
@@ -663,7 +663,7 @@ func (m *Miniredis) cmdIncrby(c *server.Peer, cmd string, args []string) {
 	withTx(m, c, func(c *server.Peer, ctx *connCtx) {
 		db := m.db(ctx.selectedDB)
 
-		if t, ok := db.keys[opts.key]; ok && t != "string" {
+		if t, ok := db.keys[opts.key]; ok && t != keyTypeString {
 			c.WriteError(msgWrongType)
 			return
 		}
@@ -703,7 +703,7 @@ func (m *Miniredis) cmdIncrbyfloat(c *server.Peer, cmd string, args []string) {
 	withTx(m, c, func(c *server.Peer, ctx *connCtx) {
 		db := m.db(ctx.selectedDB)
 
-		if t, ok := db.keys[key]; ok && t != "string" {
+		if t, ok := db.keys[key]; ok && t != keyTypeString {
 			c.WriteError(msgWrongType)
 			return
 		}
@@ -736,7 +736,7 @@ func (m *Miniredis) cmdDecr(c *server.Peer, cmd string, args []string) {
 		db := m.db(ctx.selectedDB)
 
 		key := args[0]
-		if t, ok := db.keys[key]; ok && t != "string" {
+		if t, ok := db.keys[key]; ok && t != keyTypeString {
 			c.WriteError(msgWrongType)
 			return
 		}
@@ -776,7 +776,7 @@ func (m *Miniredis) cmdDecrby(c *server.Peer, cmd string, args []string) {
 	withTx(m, c, func(c *server.Peer, ctx *connCtx) {
 		db := m.db(ctx.selectedDB)
 
-		if t, ok := db.keys[opts.key]; ok && t != "string" {
+		if t, ok := db.keys[opts.key]; ok && t != keyTypeString {
 			c.WriteError(msgWrongType)
 			return
 		}
@@ -810,7 +810,7 @@ func (m *Miniredis) cmdStrlen(c *server.Peer, cmd string, args []string) {
 	withTx(m, c, func(c *server.Peer, ctx *connCtx) {
 		db := m.db(ctx.selectedDB)
 
-		if t, ok := db.keys[key]; ok && t != "string" {
+		if t, ok := db.keys[key]; ok && t != keyTypeString {
 			c.WriteError(msgWrongType)
 			return
 		}
@@ -838,7 +838,7 @@ func (m *Miniredis) cmdAppend(c *server.Peer, cmd string, args []string) {
 	withTx(m, c, func(c *server.Peer, ctx *connCtx) {
 		db := m.db(ctx.selectedDB)
 
-		if t, ok := db.keys[key]; ok && t != "string" {
+		if t, ok := db.keys[key]; ok && t != keyTypeString {
 			c.WriteError(msgWrongType)
 			return
 		}
@@ -880,7 +880,7 @@ func (m *Miniredis) cmdGetrange(c *server.Peer, cmd string, args []string) {
 	withTx(m, c, func(c *server.Peer, ctx *connCtx) {
 		db := m.db(ctx.selectedDB)
 
-		if t, ok := db.keys[opts.key]; ok && t != "string" {
+		if t, ok := db.keys[opts.key]; ok && t != keyTypeString {
 			c.WriteError(msgWrongType)
 			return
 		}
@@ -923,7 +923,7 @@ func (m *Miniredis) cmdSetrange(c *server.Peer, cmd string, args []string) {
 	withTx(m, c, func(c *server.Peer, ctx *connCtx) {
 		db := m.db(ctx.selectedDB)
 
-		if t, ok := db.keys[opts.key]; ok && t != "string" {
+		if t, ok := db.keys[opts.key]; ok && t != keyTypeString {
 			c.WriteError(msgWrongType)
 			return
 		}
@@ -980,7 +980,7 @@ func (m *Miniredis) cmdBitcount(c *server.Peer, cmd string, args []string) {
 			c.WriteInt(0)
 			return
 		}
-		if db.t(opts.key) != "string" {
+		if db.t(opts.key) != keyTypeString {
 			c.WriteError(msgWrongType)
 			return
 		}
@@ -1030,13 +1030,13 @@ func (m *Miniredis) cmdBitop(c *server.Peer, cmd string, args []string) {
 		switch opts.op {
 		case "AND", "OR", "XOR":
 			first := opts.input[0]
-			if t, ok := db.keys[first]; ok && t != "string" {
+			if t, ok := db.keys[first]; ok && t != keyTypeString {
 				c.WriteError(msgWrongType)
 				return
 			}
 			res := []byte(db.stringKeys[first])
 			for _, vk := range opts.input[1:] {
-				if t, ok := db.keys[vk]; ok && t != "string" {
+				if t, ok := db.keys[vk]; ok && t != keyTypeString {
 					c.WriteError(msgWrongType)
 					return
 				}
@@ -1062,7 +1062,7 @@ func (m *Miniredis) cmdBitop(c *server.Peer, cmd string, args []string) {
 				return
 			}
 			key := opts.input[0]
-			if t, ok := db.keys[key]; ok && t != "string" {
+			if t, ok := db.keys[key]; ok && t != keyTypeString {
 				c.WriteError(msgWrongType)
 				return
 			}
@@ -1124,7 +1124,7 @@ func (m *Miniredis) cmdBitpos(c *server.Peer, cmd string, args []string) {
 	withTx(m, c, func(c *server.Peer, ctx *connCtx) {
 		db := m.db(ctx.selectedDB)
 
-		if t, ok := db.keys[opts.Key]; ok && t != "string" {
+		if t, ok := db.keys[opts.Key]; ok && t != keyTypeString {
 			c.WriteError(msgWrongType)
 			return
 		} else if !ok {
@@ -1215,7 +1215,7 @@ func (m *Miniredis) cmdGetbit(c *server.Peer, cmd string, args []string) {
 	withTx(m, c, func(c *server.Peer, ctx *connCtx) {
 		db := m.db(ctx.selectedDB)
 
-		if t, ok := db.keys[opts.key]; ok && t != "string" {
+		if t, ok := db.keys[opts.key]; ok && t != keyTypeString {
 			c.WriteError(msgWrongType)
 			return
 		}
@@ -1276,7 +1276,7 @@ func (m *Miniredis) cmdSetbit(c *server.Peer, cmd string, args []string) {
 	withTx(m, c, func(c *server.Peer, ctx *connCtx) {
 		db := m.db(ctx.selectedDB)
 
-		if t, ok := db.keys[opts.key]; ok && t != "string" {
+		if t, ok := db.keys[opts.key]; ok && t != keyTypeString {
 			c.WriteError(msgWrongType)
 			return
 		}
diff --git a/db.go b/db.go
index af56839..6af7ba3 100644
--- a/db.go
+++ b/db.go
@@ -70,19 +70,19 @@ func (db *RedisDB) move(key string, to *RedisDB) bool {
 	}
 	to.keys[key] = db.keys[key]
 	switch t {
-	case "string":
+	case keyTypeString:
 		to.stringKeys[key] = db.stringKeys[key]
-	case "hash":
+	case keyTypeHash:
 		to.hashKeys[key] = db.hashKeys[key]
-	case "list":
+	case keyTypeList:
 		to.listKeys[key] = db.listKeys[key]
-	case "set":
+	case keyTypeSet:
 		to.setKeys[key] = db.setKeys[key]
-	case "zset":
+	case keyTypeSortedSet:
 		to.sortedsetKeys[key] = db.sortedsetKeys[key]
-	case "stream":
+	case keyTypeStream:
 		to.streamKeys[key] = db.streamKeys[key]
-	case "hll":
+	case keyTypeHll:
 		to.hllKeys[key] = db.hllKeys[key]
 	default:
 		panic("unhandled key type")
@@ -98,19 +98,19 @@ func (db *RedisDB) move(key string, to *RedisDB) bool {
 func (db *RedisDB) rename(from, to string) {
 	db.del(to, true)
 	switch db.t(from) {
-	case "string":
+	case keyTypeString:
 		db.stringKeys[to] = db.stringKeys[from]
-	case "hash":
+	case keyTypeHash:
 		db.hashKeys[to] = db.hashKeys[from]
-	case "list":
+	case keyTypeList:
 		db.listKeys[to] = db.listKeys[from]
-	case "set":
+	case keyTypeSet:
 		db.setKeys[to] = db.setKeys[from]
-	case "zset":
+	case keyTypeSortedSet:
 		db.sortedsetKeys[to] = db.sortedsetKeys[from]
-	case "stream":
+	case keyTypeStream:
 		db.streamKeys[to] = db.streamKeys[from]
-	case "hll":
+	case keyTypeHll:
 		db.hllKeys[to] = db.hllKeys[from]
 	default:
 		panic("missing case")
@@ -136,19 +136,19 @@ func (db *RedisDB) del(k string, delTTL bool) {
 		delete(db.ttl, k)
 	}
 	switch t {
-	case "string":
+	case keyTypeString:
 		delete(db.stringKeys, k)
-	case "hash":
+	case keyTypeHash:
 		delete(db.hashKeys, k)
-	case "list":
+	case keyTypeList:
 		delete(db.listKeys, k)
-	case "set":
+	case keyTypeSet:
 		delete(db.setKeys, k)
-	case "zset":
+	case keyTypeSortedSet:
 		delete(db.sortedsetKeys, k)
-	case "stream":
+	case keyTypeStream:
 		delete(db.streamKeys, k)
-	case "hll":
+	case keyTypeHll:
 		delete(db.hllKeys, k)
 	default:
 		panic("Unknown key type: " + t)
@@ -157,7 +157,7 @@ func (db *RedisDB) del(k string, delTTL bool) {
 
 // stringGet returns the string key or "" on error/nonexists.
 func (db *RedisDB) stringGet(k string) string {
-	if t, ok := db.keys[k]; !ok || t != "string" {
+	if t, ok := db.keys[k]; !ok || t != keyTypeString {
 		return ""
 	}
 	return db.stringKeys[k]
@@ -166,7 +166,7 @@ func (db *RedisDB) stringGet(k string) string {
 // stringSet force set()s a key. Does not touch expire.
 func (db *RedisDB) stringSet(k, v string) {
 	db.del(k, false)
-	db.keys[k] = "string"
+	db.keys[k] = keyTypeString
 	db.stringKeys[k] = v
 	db.incr(k)
 }
@@ -217,7 +217,7 @@ func (db *RedisDB) stringIncrfloat(k string, delta *big.Float) (*big.Float, erro
 func (db *RedisDB) listLpush(k, v string) int {
 	l, ok := db.listKeys[k]
 	if !ok {
-		db.keys[k] = "list"
+		db.keys[k] = keyTypeList
 	}
 	l = append([]string{v}, l...)
 	db.listKeys[k] = l
@@ -242,7 +242,7 @@ func (db *RedisDB) listLpop(k string) string {
 func (db *RedisDB) listPush(k string, v ...string) int {
 	l, ok := db.listKeys[k]
 	if !ok {
-		db.keys[k] = "list"
+		db.keys[k] = keyTypeList
 	}
 	l = append(l, v...)
 	db.listKeys[k] = l
@@ -265,7 +265,7 @@ func (db *RedisDB) listPop(k string) string {
 
 // setset replaces a whole set.
 func (db *RedisDB) setSet(k string, set setKey) {
-	db.keys[k] = "set"
+	db.keys[k] = keyTypeSet
 	db.setKeys[k] = set
 	db.incr(k)
 }
@@ -275,7 +275,7 @@ func (db *RedisDB) setAdd(k string, elems ...string) int {
 	s, ok := db.setKeys[k]
 	if !ok {
 		s = setKey{}
-		db.keys[k] = "set"
+		db.keys[k] = keyTypeSet
 	}
 	added := 0
 	for _, e := range elems {
@@ -361,10 +361,10 @@ func (db *RedisDB) hashGet(key, field string) string {
 
 // hashSet returns the number of new keys
 func (db *RedisDB) hashSet(k string, fv ...string) int {
-	if t, ok := db.keys[k]; ok && t != "hash" {
+	if t, ok := db.keys[k]; ok && t != keyTypeHash {
 		db.del(k, true)
 	}
-	db.keys[k] = "hash"
+	db.keys[k] = keyTypeHash
 	if _, ok := db.hashKeys[k]; !ok {
 		db.hashKeys[k] = map[string]string{}
 	}
@@ -424,7 +424,7 @@ func (db *RedisDB) sortedSet(key string) map[string]float64 {
 
 // ssetSet sets a complete sorted set.
 func (db *RedisDB) ssetSet(key string, sset sortedSet) {
-	db.keys[key] = "zset"
+	db.keys[key] = keyTypeSortedSet
 	db.incr(key)
 	db.sortedsetKeys[key] = sset
 }
@@ -434,7 +434,7 @@ func (db *RedisDB) ssetAdd(key string, score float64, member string) bool {
 	ss, ok := db.sortedsetKeys[key]
 	if !ok {
 		ss = newSortedSet()
-		db.keys[key] = "zset"
+		db.keys[key] = keyTypeSortedSet
 	}
 	_, ok = ss[member]
 	ss[member] = score
@@ -526,7 +526,7 @@ func (db *RedisDB) ssetIncrby(k, m string, delta float64) float64 {
 	ss, ok := db.sortedsetKeys[k]
 	if !ok {
 		ss = newSortedSet()
-		db.keys[k] = "zset"
+		db.keys[k] = keyTypeSortedSet
 		db.sortedsetKeys[k] = ss
 	}
 
@@ -541,7 +541,7 @@ func (db *RedisDB) ssetIncrby(k, m string, delta float64) float64 {
 func (db *RedisDB) setDiff(keys []string) (setKey, error) {
 	key := keys[0]
 	keys = keys[1:]
-	if db.exists(key) && db.t(key) != "set" {
+	if db.exists(key) && db.t(key) != keyTypeSet {
 		return nil, ErrWrongType
 	}
 	s := setKey{}
@@ -552,7 +552,7 @@ func (db *RedisDB) setDiff(keys []string) (setKey, error) {
 		if !db.exists(sk) {
 			continue
 		}
-		if db.t(sk) != "set" {
+		if db.t(sk) != keyTypeSet {
 			return nil, ErrWrongType
 		}
 		for e := range db.setKeys[sk] {
@@ -567,7 +567,7 @@ func (db *RedisDB) setDiff(keys []string) (setKey, error) {
 func (db *RedisDB) setInter(keys []string) (setKey, error) {
 	// all keys must either not exist, or be of type "set".
 	for _, key := range keys {
-		if db.exists(key) && db.t(key) != "set" {
+		if db.exists(key) && db.t(key) != keyTypeSet {
 			return nil, ErrWrongType
 		}
 	}
@@ -577,7 +577,7 @@ func (db *RedisDB) setInter(keys []string) (setKey, error) {
 	if !db.exists(key) {
 		return nil, nil
 	}
-	if db.t(key) != "set" {
+	if db.t(key) != keyTypeSet {
 		return nil, ErrWrongType
 	}
 	s := setKey{}
@@ -588,7 +588,7 @@ func (db *RedisDB) setInter(keys []string) (setKey, error) {
 		if !db.exists(sk) {
 			return setKey{}, nil
 		}
-		if db.t(sk) != "set" {
+		if db.t(sk) != keyTypeSet {
 			return nil, ErrWrongType
 		}
 		other := db.setKeys[sk]
@@ -682,7 +682,7 @@ func (db *RedisDB) newStream(key string) (*streamKey, error) {
 		return nil, fmt.Errorf("ErrAlreadyExists")
 	}
 
-	db.keys[key] = "stream"
+	db.keys[key] = keyTypeStream
 	s := newStreamKey()
 	db.streamKeys[key] = s
 	db.incr(key)
@@ -691,7 +691,7 @@ func (db *RedisDB) newStream(key string) (*streamKey, error) {
 
 // return existing stream, or nil.
 func (db *RedisDB) stream(key string) (*streamKey, error) {
-	if db.exists(key) && db.t(key) != "stream" {
+	if db.exists(key) && db.t(key) != keyTypeStream {
 		return nil, ErrWrongType
 	}
 
@@ -728,7 +728,7 @@ func (db *RedisDB) hllAdd(k string, elems ...string) int {
 	s, ok := db.hllKeys[k]
 	if !ok {
 		s = newHll()
-		db.keys[k] = "hll"
+		db.keys[k] = keyTypeHll
 	}
 	hllAltered := 0
 	for _, e := range elems {
@@ -745,7 +745,7 @@ func (db *RedisDB) hllAdd(k string, elems ...string) int {
 func (db *RedisDB) hllCount(keys []string) (int, error) {
 	countOverall := 0
 	for _, key := range keys {
-		if db.exists(key) && db.t(key) != "hll" {
+		if db.exists(key) && db.t(key) != keyTypeHll {
 			return 0, ErrNotValidHllValue
 		}
 		if !db.exists(key) {
@@ -760,7 +760,7 @@ func (db *RedisDB) hllCount(keys []string) (int, error) {
 // hllMerge merges all the hlls provided as keys to the first key. Creates a new hll in the first key if it contains nothing
 func (db *RedisDB) hllMerge(keys []string) error {
 	for _, key := range keys {
-		if db.exists(key) && db.t(key) != "hll" {
+		if db.exists(key) && db.t(key) != keyTypeHll {
 			return ErrNotValidHllValue
 		}
 	}
@@ -783,7 +783,7 @@ func (db *RedisDB) hllMerge(keys []string) error {
 	}
 
 	db.hllKeys[destKey] = destHll
-	db.keys[destKey] = "hll"
+	db.keys[destKey] = keyTypeHll
 	db.incr(destKey)
 
 	return nil
diff --git a/direct.go b/direct.go
index 31505eb..88ef361 100644
--- a/direct.go
+++ b/direct.go
@@ -90,7 +90,7 @@ func (db *RedisDB) Get(k string) (string, error) {
 	if !db.exists(k) {
 		return "", ErrKeyNotFound
 	}
-	if db.t(k) != "string" {
+	if db.t(k) != keyTypeString {
 		return "", ErrWrongType
 	}
 	return db.stringGet(k), nil
@@ -108,7 +108,7 @@ func (db *RedisDB) Set(k, v string) error {
 	defer db.master.Unlock()
 	defer db.master.signal.Broadcast()
 
-	if db.exists(k) && db.t(k) != "string" {
+	if db.exists(k) && db.t(k) != keyTypeString {
 		return ErrWrongType
 	}
 	db.del(k, true) // Remove expire
@@ -127,7 +127,7 @@ func (db *RedisDB) Incr(k string, delta int) (int, error) {
 	defer db.master.Unlock()
 	defer db.master.signal.Broadcast()
 
-	if db.exists(k) && db.t(k) != "string" {
+	if db.exists(k) && db.t(k) != keyTypeString {
 		return 0, ErrWrongType
 	}
 
@@ -151,7 +151,7 @@ func (db *RedisDB) Incrfloat(k string, delta float64) (float64, error) {
 	defer db.master.Unlock()
 	defer db.master.signal.Broadcast()
 
-	if db.exists(k) && db.t(k) != "string" {
+	if db.exists(k) && db.t(k) != keyTypeString {
 		return 0, ErrWrongType
 	}
 
@@ -180,7 +180,7 @@ func (db *RedisDB) List(k string) ([]string, error) {
 	if !db.exists(k) {
 		return nil, ErrKeyNotFound
 	}
-	if db.t(k) != "list" {
+	if db.t(k) != keyTypeList {
 		return nil, ErrWrongType
 	}
 	return db.listKeys[k], nil
@@ -197,7 +197,7 @@ func (db *RedisDB) Lpush(k, v string) (int, error) {
 	defer db.master.Unlock()
 	defer db.master.signal.Broadcast()
 
-	if db.exists(k) && db.t(k) != "list" {
+	if db.exists(k) && db.t(k) != keyTypeList {
 		return 0, ErrWrongType
 	}
 	return db.listLpush(k, v), nil
@@ -217,7 +217,7 @@ func (db *RedisDB) Lpop(k string) (string, error) {
 	if !db.exists(k) {
 		return "", ErrKeyNotFound
 	}
-	if db.t(k) != "list" {
+	if db.t(k) != keyTypeList {
 		return "", ErrWrongType
 	}
 	return db.listLpop(k), nil
@@ -240,7 +240,7 @@ func (db *RedisDB) Push(k string, v ...string) (int, error) {
 	defer db.master.Unlock()
 	defer db.master.signal.Broadcast()
 
-	if db.exists(k) && db.t(k) != "list" {
+	if db.exists(k) && db.t(k) != keyTypeList {
 		return 0, ErrWrongType
 	}
 	return db.listPush(k, v...), nil
@@ -265,7 +265,7 @@ func (db *RedisDB) Pop(k string) (string, error) {
 	if !db.exists(k) {
 		return "", ErrKeyNotFound
 	}
-	if db.t(k) != "list" {
+	if db.t(k) != keyTypeList {
 		return "", ErrWrongType
 	}
 
@@ -289,7 +289,7 @@ func (db *RedisDB) SetAdd(k string, elems ...string) (int, error) {
 	defer db.master.Unlock()
 	defer db.master.signal.Broadcast()
 
-	if db.exists(k) && db.t(k) != "set" {
+	if db.exists(k) && db.t(k) != keyTypeSet {
 		return 0, ErrWrongType
 	}
 	return db.setAdd(k, elems...), nil
@@ -314,7 +314,7 @@ func (db *RedisDB) Members(k string) ([]string, error) {
 	if !db.exists(k) {
 		return nil, ErrKeyNotFound
 	}
-	if db.t(k) != "set" {
+	if db.t(k) != keyTypeSet {
 		return nil, ErrWrongType
 	}
 	return db.setMembers(k), nil
@@ -339,7 +339,7 @@ func (db *RedisDB) IsMember(k, v string) (bool, error) {
 	if !db.exists(k) {
 		return false, ErrKeyNotFound
 	}
-	if db.t(k) != "set" {
+	if db.t(k) != keyTypeSet {
 		return false, ErrWrongType
 	}
 	return db.setIsMember(k, v), nil
@@ -358,7 +358,7 @@ func (db *RedisDB) HKeys(key string) ([]string, error) {
 	if !db.exists(key) {
 		return nil, ErrKeyNotFound
 	}
-	if db.t(key) != "hash" {
+	if db.t(key) != keyTypeHash {
 		return nil, ErrWrongType
 	}
 	return db.hashFields(key), nil
@@ -569,7 +569,7 @@ func (db *RedisDB) SRem(k string, fields ...string) (int, error) {
 	if !db.exists(k) {
 		return 0, ErrKeyNotFound
 	}
-	if db.t(k) != "set" {
+	if db.t(k) != keyTypeSet {
 		return 0, ErrWrongType
 	}
 	return db.setRem(k, fields...), nil
@@ -586,7 +586,7 @@ func (db *RedisDB) ZAdd(k string, score float64, member string) (bool, error) {
 	defer db.master.Unlock()
 	defer db.master.signal.Broadcast()
 
-	if db.exists(k) && db.t(k) != "zset" {
+	if db.exists(k) && db.t(k) != keyTypeSortedSet {
 		return false, ErrWrongType
 	}
 	return db.ssetAdd(k, score, member), nil
@@ -605,7 +605,7 @@ func (db *RedisDB) ZMembers(k string) ([]string, error) {
 	if !db.exists(k) {
 		return nil, ErrKeyNotFound
 	}
-	if db.t(k) != "zset" {
+	if db.t(k) != keyTypeSortedSet {
 		return nil, ErrWrongType
 	}
 	return db.ssetMembers(k), nil
@@ -624,7 +624,7 @@ func (db *RedisDB) SortedSet(k string) (map[string]float64, error) {
 	if !db.exists(k) {
 		return nil, ErrKeyNotFound
 	}
-	if db.t(k) != "zset" {
+	if db.t(k) != keyTypeSortedSet {
 		return nil, ErrWrongType
 	}
 	return db.sortedSet(k), nil
@@ -644,7 +644,7 @@ func (db *RedisDB) ZRem(k, member string) (bool, error) {
 	if !db.exists(k) {
 		return false, ErrKeyNotFound
 	}
-	if db.t(k) != "zset" {
+	if db.t(k) != keyTypeSortedSet {
 		return false, ErrWrongType
 	}
 	return db.ssetRem(k, member), nil
@@ -663,7 +663,7 @@ func (db *RedisDB) ZScore(k, member string) (float64, error) {
 	if !db.exists(k) {
 		return 0, ErrKeyNotFound
 	}
-	if db.t(k) != "zset" {
+	if db.t(k) != keyTypeSortedSet {
 		return 0, ErrWrongType
 	}
 	return db.ssetScore(k, member), nil
@@ -681,7 +681,7 @@ func (db *RedisDB) ZMScore(k string, members []string) ([]float64, error) {
 	if !db.exists(k) {
 		return nil, ErrKeyNotFound
 	}
-	if db.t(k) != "zset" {
+	if db.t(k) != keyTypeSortedSet {
 		return nil, ErrWrongType
 	}
 	return db.ssetMScore(k, members), nil
@@ -783,7 +783,7 @@ func (db *RedisDB) HllAdd(k string, elems ...string) (int, error) {
 	db.master.Lock()
 	defer db.master.Unlock()
 
-	if db.exists(k) && db.t(k) != "hll" {
+	if db.exists(k) && db.t(k) != keyTypeHll {
 		return 0, ErrWrongType
 	}
 	return db.hllAdd(k, elems...), nil
diff --git a/miniredis.go b/miniredis.go
index a9600ef..6996872 100644
--- a/miniredis.go
+++ b/miniredis.go
@@ -404,25 +404,25 @@ func (m *Miniredis) Dump() string {
 		r += fmt.Sprintf("- %s\n", k)
 		t := db.t(k)
 		switch t {
-		case "string":
+		case keyTypeString:
 			r += fmt.Sprintf("%s%s\n", indent, v(db.stringKeys[k]))
-		case "hash":
+		case keyTypeHash:
 			for _, hk := range db.hashFields(k) {
 				r += fmt.Sprintf("%s%s: %s\n", indent, hk, v(db.hashGet(k, hk)))
 			}
-		case "list":
+		case keyTypeList:
 			for _, lk := range db.listKeys[k] {
 				r += fmt.Sprintf("%s%s\n", indent, v(lk))
 			}
-		case "set":
+		case keyTypeSet:
 			for _, mk := range db.setMembers(k) {
 				r += fmt.Sprintf("%s%s\n", indent, v(mk))
 			}
-		case "zset":
+		case keyTypeSortedSet:
 			for _, el := range db.ssetElements(k) {
 				r += fmt.Sprintf("%s%f: %s\n", indent, el.score, v(el.member))
 			}
-		case "stream":
+		case keyTypeStream:
 			for _, entry := range db.streamKeys[k].entries {
 				r += fmt.Sprintf("%s%s\n", indent, entry.ID)
 				ev := entry.Values
@@ -430,7 +430,7 @@ func (m *Miniredis) Dump() string {
 					r += fmt.Sprintf("%s%s%s: %s\n", indent, indent, v(ev[2*i]), v(ev[2*i+1]))
 				}
 			}
-		case "hll":
+		case keyTypeHll:
 			for _, entry := range db.hllKeys {
 				r += fmt.Sprintf("%s%s\n", indent, v(string(entry.Bytes())))
 			}
@@ -703,19 +703,19 @@ func (m *Miniredis) copy(
 	}
 
 	switch srcDB.t(src) {
-	case "string":
+	case keyTypeString:
 		destDB.stringKeys[dst] = srcDB.stringKeys[src]
-	case "hash":
+	case keyTypeHash:
 		destDB.hashKeys[dst] = copyHashKey(srcDB.hashKeys[src])
-	case "list":
+	case keyTypeList:
 		destDB.listKeys[dst] = copyListKey(srcDB.listKeys[src])
-	case "set":
+	case keyTypeSet:
 		destDB.setKeys[dst] = copySetKey(srcDB.setKeys[src])
-	case "zset":
+	case keyTypeSortedSet:
 		destDB.sortedsetKeys[dst] = copySortedSet(srcDB.sortedsetKeys[src])
-	case "stream":
+	case keyTypeStream:
 		destDB.streamKeys[dst] = srcDB.streamKeys[src].copy()
-	case "hll":
+	case keyTypeHll:
 		destDB.hllKeys[dst] = srcDB.hllKeys[src].copy()
 	default:
 		panic("missing case")
diff --git a/redis.go b/redis.go
index f70728e..2bf3bae 100644
--- a/redis.go
+++ b/redis.go
@@ -12,6 +12,16 @@ import (
 	"github.com/alicebob/miniredis/v2/server"
 )
 
+const (
+	keyTypeString    = "string"
+	keyTypeHash      = "hash"
+	keyTypeList      = "list"
+	keyTypeSet       = "set"
+	keyTypeHll       = "hll"
+	keyTypeSortedSet = "zset"
+	keyTypeStream    = "stream"
+)
+
 const (
 	msgWrongType            = "WRONGTYPE Operation against a key holding the wrong kind of value"
 	msgNotValidHllValue     = "WRONGTYPE Key is not a valid HyperLogLog string value."