diff --git a/src/effect/schema/class/MutableClass.ts b/src/effect/schema/class/MutableClass.ts
index c21aa1e..8d31f96 100644
--- a/src/effect/schema/class/MutableClass.ts
+++ b/src/effect/schema/class/MutableClass.ts
@@ -1,25 +1,21 @@
 import { Schema as S } from "@effect/schema"
 import type { Annotations, Struct } from "@effect/schema/Schema"
 import type { TMutableClass } from "./TMutableClass"
-import type { HasFields, MissingSelfGeneric } from "./util"
+import type { HasFields } from "./util"
 
 
 export function MutableClass<Self = never>(identifier: string) {
     return <Fields extends Struct.Fields>(
         fieldsOr:      Fields | HasFields<Fields>,
         annotations?:  Annotations.Schema<Self>,
-    ): (
-        [Self] extends [never]
-            ? MissingSelfGeneric<"Class">
-            : TMutableClass<
-                Self,
-                Fields,
-                Struct.Encoded<Fields>,
-                Struct.Context<Fields>,
-                Struct.Constructor<Fields>,
-                {},
-                {}
-            >
     ) =>
-        S.Class<Self>(identifier)(fieldsOr, annotations)
+        S.Class<Self>(identifier)(fieldsOr, annotations) as TMutableClass<
+            Self,
+            Fields,
+            Struct.Encoded<Fields>,
+            Struct.Context<Fields>,
+            Struct.Constructor<Fields>,
+            {},
+            {}
+        >
 }
diff --git a/src/effect/schema/class/tests.ts b/src/effect/schema/class/tests.ts
index 40fd657..0207522 100644
--- a/src/effect/schema/class/tests.ts
+++ b/src/effect/schema/class/tests.ts
@@ -1,5 +1,18 @@
 import { Schema as S } from "@effect/schema"
 import { MutableClass } from "./MutableClass"
+import { pipe } from "remeda"
+import { Mutable } from "./Mutable"
+import { MobXObservable } from "./MobXObservable"
+
+
+const UserSuper = <Self>() => pipe(
+    MutableClass<Self>("User")({
+        id: S.BigIntFromSelf,
+        role: S.Union(S.Literal("BasicUser"), S.Literal("Admin")),
+    }),
+
+    v => MobXObservable(v),
+)
 
 
 class User extends MutableClass<User>("User")({