diff --git a/packages/amplify_datastore/example/ios/unit_tests/GraphQLResponse+DecodeTests.swift b/packages/amplify_datastore/example/ios/unit_tests/GraphQLResponse+DecodeTests.swift
index 3c5d1071af..c046b6c341 100644
--- a/packages/amplify_datastore/example/ios/unit_tests/GraphQLResponse+DecodeTests.swift
+++ b/packages/amplify_datastore/example/ios/unit_tests/GraphQLResponse+DecodeTests.swift
@@ -116,7 +116,7 @@ class GraphQLResponseDecodeTests: XCTestCase {
             "a": ["b"]
         ]
         let expectedJson = "{\"a\":[\"b\"]}"
-        let result: Result<String, APIError> = GraphQLResponse<String>.decodeDataPayload(json, modelName: nil)
+        let result: Result<String, APIError> = GraphQLResponse<String>.decodeDataPayload(json, modelName: "Post")
         XCTAssertNoThrow(try result.get())
         XCTAssertEqual(expectedJson, try result.get())
     }
@@ -137,7 +137,7 @@ class GraphQLResponseDecodeTests: XCTestCase {
             "author": "authorId",
         ], modelName: "Post"))
 
-        let result: Result<AnyModel, APIError> = GraphQLResponse<AnyModel>.decodeDataPayload(json, modelName: nil)
+        let result: Result<AnyModel, APIError> = GraphQLResponse<AnyModel>.decodeDataPayload(json, modelName: "Post")
         XCTAssertNoThrow(try result.get())
         XCTAssertEqual(expectedModel.modelName, try result.get().modelName)
         XCTAssertEqual(expectedModel.id, try result.get().id)
@@ -227,7 +227,11 @@ class GraphQLResponseDecodeTests: XCTestCase {
             "author": "authorId",
         ], modelName: "Post"))
 
-        let result: Result<GraphQLResponse<MutationSync<AnyModel>>, APIError> = .fromAppSyncResponse(json: json, decodePath: "onCreatePost", modelName: nil)
+        let result: Result<GraphQLResponse<MutationSync<AnyModel>>, APIError> = .fromAppSyncResponse(
+            json: json,
+            decodePath: "onCreatePost",
+            modelName: "Post"
+        )
         XCTAssertNoThrow(try result.get())
         let mutationSync = try! result.get()
         XCTAssertNoThrow(try mutationSync.get())
@@ -244,7 +248,11 @@ class GraphQLResponseDecodeTests: XCTestCase {
             ]
         ]
 
-        let result: Result<GraphQLResponse<MutationSync<AnyModel>>, APIError> = .fromAppSyncResponse(json: json, decodePath: "onCreatePost", modelName: nil)
+        let result: Result<GraphQLResponse<MutationSync<AnyModel>>, APIError> = .fromAppSyncResponse(
+            json: json,
+            decodePath: "onCreatePost",
+            modelName: "Post"
+        )
         XCTAssertNoThrow(try result.get())
         let mutationSync = try! result.get()
         XCTAssertThrowsError(try mutationSync.get()) { error in
@@ -283,7 +291,11 @@ class GraphQLResponseDecodeTests: XCTestCase {
             "author": "authorId",
         ], modelName: "Post"))
 
-        let result: Result<GraphQLResponse<MutationSync<AnyModel>>, APIError> = .fromAppSyncResponse(json: json, decodePath: "onCreatePost", modelName: nil)
+        let result: Result<GraphQLResponse<MutationSync<AnyModel>>, APIError> = .fromAppSyncResponse(
+            json: json,
+            decodePath: "onCreatePost",
+            modelName: "Post"
+        )
         XCTAssertNoThrow(try result.get())
         let mutationSync = try! result.get()
         XCTAssertThrowsError(try mutationSync.get()) { error in
@@ -305,7 +317,11 @@ class GraphQLResponseDecodeTests: XCTestCase {
             "a": "b"
         ]
 
-        let result: Result<GraphQLResponse<MutationSync<AnyModel>>, APIError> = .fromAppSyncResponse(json: json, decodePath: "onCreatePost", modelName: nil)
+        let result: Result<GraphQLResponse<MutationSync<AnyModel>>, APIError> = .fromAppSyncResponse(
+            json: json,
+            decodePath: "onCreatePost",
+            modelName: "Post"
+        )
         XCTAssertThrowsError(try result.get()) { error in
             if case .unknown(let description, _, _) = (error as! APIError) {
                 XCTAssertEqual("Failed to get data object or errors from GraphQL response", description)
@@ -325,7 +341,7 @@ class GraphQLResponseDecodeTests: XCTestCase {
         ]
 
         let jsonString = String(data: try! JSONEncoder().encode(json), encoding: .utf8)!
-        let response: GraphQLResponse<AnyModel> = .fromAppSyncResponse(string: jsonString, decodePath: nil)
+        let response: GraphQLResponse<AnyModel> = .fromAppSyncResponse(string: jsonString, decodePath: nil, modelName: "Post")
         XCTAssertNoThrow(try response.get())
         XCTAssertEqual(json.id?.stringValue, try response.get().identifier)
         XCTAssertEqual(json.__typename?.stringValue, try response.get().modelName)
@@ -334,7 +350,7 @@ class GraphQLResponseDecodeTests: XCTestCase {
     func testFromAppSyncResponse_withBrokenJsonString_failWithTransformationError() {
         SchemaData.modelSchemaRegistry.registerModels(registry: ModelRegistry.self)
         let jsonString = "{"
-        let response: GraphQLResponse<AnyModel> = .fromAppSyncResponse(string: jsonString, decodePath: nil)
+        let response: GraphQLResponse<AnyModel> = .fromAppSyncResponse(string: jsonString, decodePath: nil, modelName: "Post")
         XCTAssertThrowsError(try response.get()) { error in
             guard case .transformationError = error as! GraphQLResponseError<AnyModel> else {
                 XCTFail("Should failed with transformationError")
@@ -358,7 +374,11 @@ class GraphQLResponseDecodeTests: XCTestCase {
         ]
 
         let jsonString = String(data: try! JSONEncoder().encode(payloadJson), encoding: .utf8)!
-        let response: GraphQLResponse<MutationSync<AnyModel>> = .fromAppSyncResponse(string: jsonString, decodePath: "onCreatePost")
+        let response: GraphQLResponse<MutationSync<AnyModel>> = .fromAppSyncResponse(
+            string: jsonString,
+            decodePath: "onCreatePost",
+            modelName: "Post"
+        )
         XCTAssertNoThrow(try response.get())
         let mutationSync = try! response.get()
         XCTAssertEqual(payloadJson.onCreatePost?.id?.stringValue, mutationSync.model.identifier)
@@ -368,7 +388,11 @@ class GraphQLResponseDecodeTests: XCTestCase {
     func testFromAppSyncSubscriptionResponse_withWrongJsonString_failWithTransformationError() {
         SchemaData.modelSchemaRegistry.registerModels(registry: ModelRegistry.self)
         let jsonString = "{"
-        let response: GraphQLResponse<MutationSync<AnyModel>> = .fromAppSyncSubscriptionResponse(string: jsonString, decodePath: nil)
+        let response: GraphQLResponse<MutationSync<AnyModel>> = .fromAppSyncSubscriptionResponse(
+            string: jsonString,
+            decodePath: nil,
+            modelName: "Post"
+        )
         XCTAssertThrowsError(try response.get()) { error in
             guard case .transformationError = error as! GraphQLResponseError<MutationSync<AnyModel>> else {
                 XCTFail("Should failed with transformationError")
diff --git a/packages/amplify_datastore/ios/Classes/FlutterApiPlugin.swift b/packages/amplify_datastore/ios/Classes/FlutterApiPlugin.swift
index b23182c352..0ceb6ffa02 100644
--- a/packages/amplify_datastore/ios/Classes/FlutterApiPlugin.swift
+++ b/packages/amplify_datastore/ios/Classes/FlutterApiPlugin.swift
@@ -100,12 +100,14 @@ public class FlutterApiPlugin: APICategoryPlugin
             throw DataStoreError.decodingError("Request payload could not be empty", "")
         }
         
-        let datastoreOptions = request.options?.pluginOptions as? AWSAPIPluginDataStoreOptions
-        
+        guard let datastoreOptions = request.options?.pluginOptions as? AWSAPIPluginDataStoreOptions else {
+            throw DataStoreError.decodingError("Failed to decode the GraphQLRequest due to a missing options field.", "")
+        }
+
         return GraphQLResponse<R>.fromAppSyncResponse(
             string: payload,
             decodePath: request.decodePath,
-            modelName: datastoreOptions?.modelName
+            modelName: datastoreOptions.modelName
         )
     }
 
@@ -117,12 +119,14 @@ public class FlutterApiPlugin: APICategoryPlugin
             throw DataStoreError.decodingError("Request payload could not be empty", "")
         }
         
-        let datastoreOptions = request.options?.pluginOptions as? AWSAPIPluginDataStoreOptions
+        guard let datastoreOptions = request.options?.pluginOptions as? AWSAPIPluginDataStoreOptions else {
+            throw DataStoreError.decodingError("Failed to decode the GraphQLRequest due to a missing options field.", "")
+        }
 
         return GraphQLResponse<R>.fromAppSyncSubscriptionResponse(
             string: payload,
             decodePath: request.decodePath,
-            modelName: datastoreOptions?.modelName
+            modelName: datastoreOptions.modelName
         )
     }
     
diff --git a/packages/amplify_datastore/ios/Classes/api/GraphQLResponse+Decode.swift b/packages/amplify_datastore/ios/Classes/api/GraphQLResponse+Decode.swift
index acb977c8e4..630fdd0636 100644
--- a/packages/amplify_datastore/ios/Classes/api/GraphQLResponse+Decode.swift
+++ b/packages/amplify_datastore/ios/Classes/api/GraphQLResponse+Decode.swift
@@ -22,7 +22,7 @@ extension GraphQLResponse {
     public static func fromAppSyncResponse<R: Decodable>(
         string: String,
         decodePath: String?,
-        modelName: String? = nil
+        modelName: String
     ) -> GraphQLResponse<R> {
         guard let data = string.data(using: .utf8) else {
             return .failure(.transformationError(
@@ -44,7 +44,7 @@ extension GraphQLResponse {
     public static func fromAppSyncSubscriptionResponse<R: Decodable>(
         string: String,
         decodePath: String?,
-        modelName: String? = nil
+        modelName: String
     ) -> GraphQLResponse<R> {
         guard let data = string.data(using: .utf8) else {
             return .failure(.transformationError(
@@ -98,7 +98,7 @@ extension GraphQLResponse {
     static func fromAppSyncResponse<R: Decodable>(
         json: JSONValue,
         decodePath: String?,
-        modelName: String?
+        modelName: String
     ) -> Result<GraphQLResponse<R>, APIError> {
         let data = decodePath != nil ? json.value(at: decodePath!) : json
         let errors = json.errors?.asArray
@@ -147,18 +147,17 @@ extension GraphQLResponse {
 
     static func decodeDataPayload<R: Decodable>(
         _ dataPayload: JSONValue,
-        modelName: String?
+        modelName: String
     ) -> Result<R, APIError> {
         if R.self == String.self {
             return encodeDataPayloadToString(dataPayload).map { $0 as! R }
         }
         
         /// This is included to allow multi-platform support. Requests that do not have `__typename` 
-        let dataPayloadWithTypeName = modelName.flatMap {
-            dataPayload.asObject?.merging(
-                ["__typename": .string($0)]
-            ) { a, _ in a }
-        }.map { JSONValue.object($0) } ?? dataPayload
+        let dataPayloadWithTypeName = (dataPayload.asObject?.merging(
+            ["__typename": .string(modelName)],
+            uniquingKeysWith: { a, _ in a }
+        )).map { JSONValue.object($0) } ?? dataPayload
 
         if R.self == AnyModel.self {
             return decodeDataPayloadToAnyModel(dataPayloadWithTypeName).map { $0 as! R }