diff --git a/field_map.go b/field_map.go
index 18216f81c..f17fae9ff 100644
--- a/field_map.go
+++ b/field_map.go
@@ -128,6 +128,16 @@ func (m FieldMap) GetBytes(tag Tag) ([]byte, MessageRejectError) {
 	return f[0].value, nil
 }
 
+// getBytesNoLock is a lock free zero-copy GetField wrapper for []bytes fields.
+func (m FieldMap) getBytesNoLock(tag Tag) ([]byte, MessageRejectError) {
+	f, ok := m.tagLookup[tag]
+	if !ok {
+		return nil, ConditionallyRequiredFieldMissing(tag)
+	}
+
+	return f[0].value, nil
+}
+
 // GetBool is a GetField wrapper for bool fields.
 func (m FieldMap) GetBool(tag Tag) (bool, MessageRejectError) {
 	var val FIXBoolean
@@ -152,6 +162,21 @@ func (m FieldMap) GetInt(tag Tag) (int, MessageRejectError) {
 	return int(val), err
 }
 
+// GetInt is a lock free GetField wrapper for int fields.
+func (m FieldMap) getIntNoLock(tag Tag) (int, MessageRejectError) {
+	bytes, err := m.getBytesNoLock(tag)
+	if err != nil {
+		return 0, err
+	}
+
+	var val FIXInt
+	if val.Read(bytes) != nil {
+		err = IncorrectDataFormatForValue(tag)
+	}
+
+	return int(val), err
+}
+
 // GetTime is a GetField wrapper for utc timestamp fields.
 func (m FieldMap) GetTime(tag Tag) (t time.Time, err MessageRejectError) {
 	m.rwLock.RLock()
@@ -263,9 +288,6 @@ func (m *FieldMap) CopyInto(to *FieldMap) {
 }
 
 func (m *FieldMap) add(f field) {
-	m.rwLock.Lock()
-	defer m.rwLock.Unlock()
-
 	t := fieldTag(f)
 	if _, ok := m.tagLookup[t]; !ok {
 		m.tags = append(m.tags, t)
diff --git a/message.go b/message.go
index 11afd7669..75faeb85a 100644
--- a/message.go
+++ b/message.go
@@ -186,6 +186,13 @@ func doParsing(mp *msgParser) (err error) {
 	mp.msg.Body.Clear()
 	mp.msg.Trailer.Clear()
 
+	mp.msg.Header.rwLock.Lock()
+	defer mp.msg.Header.rwLock.Unlock()
+	mp.msg.Body.rwLock.Lock()
+	defer mp.msg.Body.rwLock.Unlock()
+	mp.msg.Trailer.rwLock.Lock()
+	defer mp.msg.Trailer.rwLock.Unlock()
+
 	// Allocate expected message fields in one chunk.
 	fieldCount := 0
 	for _, b := range mp.rawBytes {
@@ -267,7 +274,7 @@ func doParsing(mp *msgParser) (err error) {
 		}
 
 		if mp.parsedFieldBytes.tag == tagXMLDataLen {
-			xmlDataLen, _ = mp.msg.Header.GetInt(tagXMLDataLen)
+			xmlDataLen, _ = mp.msg.Header.getIntNoLock(tagXMLDataLen)
 		}
 		mp.fieldIndex++
 	}
@@ -292,7 +299,7 @@ func doParsing(mp *msgParser) (err error) {
 		}
 	}
 
-	bodyLength, err := mp.msg.Header.GetInt(tagBodyLength)
+	bodyLength, err := mp.msg.Header.getIntNoLock(tagBodyLength)
 	if err != nil {
 		err = parseError{OrigError: err.Error()}
 	} else if length != bodyLength && !xmlDataMsg {