diff --git a/json_serializable/CHANGELOG.md b/json_serializable/CHANGELOG.md
index 8d13284ee..849110984 100644
--- a/json_serializable/CHANGELOG.md
+++ b/json_serializable/CHANGELOG.md
@@ -1,5 +1,6 @@
-## 6.4.1-dev
+## 6.4.1
 
+- Fixed a bug when an `@JsonSerializable` class uses a mixin with fields.
 - Added more documentation `@JsonEnum`.
 
 ## 6.4.0
diff --git a/json_serializable/lib/src/field_helpers.dart b/json_serializable/lib/src/field_helpers.dart
index d07f45d2e..3e3643915 100644
--- a/json_serializable/lib/src/field_helpers.dart
+++ b/json_serializable/lib/src/field_helpers.dart
@@ -36,8 +36,9 @@ class _FieldSet implements Comparable<_FieldSet> {
   int compareTo(_FieldSet other) => _sortByLocation(sortField, other.sortField);
 
   static int _sortByLocation(FieldElement a, FieldElement b) {
-    final checkerA =
-        TypeChecker.fromStatic((a.enclosingElement3 as ClassElement).thisType);
+    final checkerA = TypeChecker.fromStatic(
+      (a.enclosingElement3 as InterfaceElement).thisType,
+    );
 
     if (!checkerA.isExactly(b.enclosingElement3)) {
       // in this case, you want to prioritize the enclosingElement that is more
diff --git a/json_serializable/pubspec.yaml b/json_serializable/pubspec.yaml
index 0a373aada..c4eef479b 100644
--- a/json_serializable/pubspec.yaml
+++ b/json_serializable/pubspec.yaml
@@ -1,5 +1,5 @@
 name: json_serializable
-version: 6.4.1-dev
+version: 6.4.1
 description: >-
   Automatically generate code for converting to and from JSON by annotating
   Dart classes.
diff --git a/json_serializable/test/integration/json_test_example.dart b/json_serializable/test/integration/json_test_example.dart
index 8d29a26f3..09c4aa6d0 100644
--- a/json_serializable/test/integration/json_test_example.dart
+++ b/json_serializable/test/integration/json_test_example.dart
@@ -239,3 +239,21 @@ class PrivateConstructor {
   bool operator ==(Object other) =>
       other is PrivateConstructor && id == other.id && value == other.value;
 }
+
+mixin RegressionTestIssue1210Mixin {
+  bool? get someProperty => null;
+
+  @override
+  int get hashCode => identityHashCode(this);
+}
+
+@JsonSerializable()
+class RegressionTestIssue1210 with RegressionTestIssue1210Mixin {
+  const RegressionTestIssue1210(this.field);
+
+  factory RegressionTestIssue1210.fromJson(Map<String, dynamic> json) =>
+      _$RegressionTestIssue1210FromJson(json);
+  final String field;
+
+  Map<String, dynamic> toJson() => _$RegressionTestIssue1210ToJson(this);
+}
diff --git a/json_serializable/test/integration/json_test_example.g.dart b/json_serializable/test/integration/json_test_example.g.dart
index 432455f76..4681280b8 100644
--- a/json_serializable/test/integration/json_test_example.g.dart
+++ b/json_serializable/test/integration/json_test_example.g.dart
@@ -213,3 +213,15 @@ Map<String, dynamic> _$PrivateConstructorToJson(PrivateConstructor instance) =>
       'id': instance.id,
       'value': instance.value,
     };
+
+RegressionTestIssue1210 _$RegressionTestIssue1210FromJson(
+        Map<String, dynamic> json) =>
+    RegressionTestIssue1210(
+      json['field'] as String,
+    );
+
+Map<String, dynamic> _$RegressionTestIssue1210ToJson(
+        RegressionTestIssue1210 instance) =>
+    <String, dynamic>{
+      'field': instance.field,
+    };
diff --git a/json_serializable/test/integration/json_test_example.g_any_map.dart b/json_serializable/test/integration/json_test_example.g_any_map.dart
index 38c5d3687..9c449727d 100644
--- a/json_serializable/test/integration/json_test_example.g_any_map.dart
+++ b/json_serializable/test/integration/json_test_example.g_any_map.dart
@@ -247,3 +247,23 @@ class PrivateConstructor {
   bool operator ==(Object other) =>
       other is PrivateConstructor && id == other.id && value == other.value;
 }
+
+mixin RegressionTestIssue1210Mixin {
+  bool? get someProperty => null;
+
+  @override
+  int get hashCode => identityHashCode(this);
+}
+
+@JsonSerializable(
+  anyMap: true,
+)
+class RegressionTestIssue1210 with RegressionTestIssue1210Mixin {
+  const RegressionTestIssue1210(this.field);
+
+  factory RegressionTestIssue1210.fromJson(Map<String, dynamic> json) =>
+      _$RegressionTestIssue1210FromJson(json);
+  final String field;
+
+  Map<String, dynamic> toJson() => _$RegressionTestIssue1210ToJson(this);
+}
diff --git a/json_serializable/test/integration/json_test_example.g_any_map.g.dart b/json_serializable/test/integration/json_test_example.g_any_map.g.dart
index 13390d797..1e86e1fbc 100644
--- a/json_serializable/test/integration/json_test_example.g_any_map.g.dart
+++ b/json_serializable/test/integration/json_test_example.g_any_map.g.dart
@@ -211,3 +211,14 @@ Map<String, dynamic> _$PrivateConstructorToJson(PrivateConstructor instance) =>
       'id': instance.id,
       'value': instance.value,
     };
+
+RegressionTestIssue1210 _$RegressionTestIssue1210FromJson(Map json) =>
+    RegressionTestIssue1210(
+      json['field'] as String,
+    );
+
+Map<String, dynamic> _$RegressionTestIssue1210ToJson(
+        RegressionTestIssue1210 instance) =>
+    <String, dynamic>{
+      'field': instance.field,
+    };