diff --git a/src/effect/schema/class/MutableClass.ts b/src/effect/schema/class/MutableClass.ts
index 8ab537b..38c14b5 100644
--- a/src/effect/schema/class/MutableClass.ts
+++ b/src/effect/schema/class/MutableClass.ts
@@ -1,7 +1,7 @@
 import { Schema as S } from "@effect/schema"
 import type { Annotations, Class, Struct } from "@effect/schema/Schema"
+import type { Mutable } from "effect/Types"
 import type { StaticType } from "../../../StaticType"
-import type { TMutableClass } from "./TMutableClass"
 import type { HasFields } from "./util"
 
 
@@ -17,7 +17,26 @@ extends Omit<
     "extend"
 >
 {
+    new(
+        ...args: ConstructorParameters<Class<Self, Fields, I, R, C, Inherited, Proto>>
+    ): Omit<
+        InstanceType<Class<Self, Fields, I, R, C, Inherited, Proto>>,
+        keyof Fields
+    > &
+    Mutable<Struct.Type<Fields>>
 
+    extend<Extended>(identifier: string): <newFields extends Struct.Fields>(
+        fields:        newFields | HasFields<newFields>,
+        annotations?:  Annotations.Schema<Extended>,
+    ) => IMutableClass<
+        Extended,
+        Fields & newFields,
+        I & Struct.Encoded<newFields>,
+        R | Struct.Context<newFields>,
+        C & Struct.Constructor<newFields>,
+        Self,
+        Proto
+    >
 }
 
 
@@ -26,7 +45,7 @@ export function MutableClass<Self>(identifier: string) {
         fieldsOr:      Fields | HasFields<Fields>,
         annotations?:  Annotations.Schema<Self>,
     ) =>
-        S.Class<Self>(identifier)(fieldsOr, annotations) as TMutableClass<
+        S.Class<Self>(identifier)(fieldsOr, annotations) as IMutableClass<
             Self,
             Fields,
             Struct.Encoded<Fields>,
diff --git a/src/effect/schema/class/index.ts b/src/effect/schema/class/index.ts
index fa8edb0..c099da4 100644
--- a/src/effect/schema/class/index.ts
+++ b/src/effect/schema/class/index.ts
@@ -2,5 +2,5 @@ export { Class } from "./Class"
 export { MobXObservable } from "./MobXObservable"
 export { Mutable } from "./Mutable"
 export { MutableClass } from "./MutableClass"
-export type { TMutableClass } from "./TMutableClass"
+export type { IMutableClass } from "./MutableClass"
 export { TaggedClass } from "./TaggedClass"
diff --git a/src/effect/schema/class/tests.ts b/src/effect/schema/class/tests.ts
index ddad564..60fe28c 100644
--- a/src/effect/schema/class/tests.ts
+++ b/src/effect/schema/class/tests.ts
@@ -8,14 +8,14 @@ import { TaggedClass } from "./TaggedClass"
 
 
 const UserSuper = <Self>() => pipe(
-    // Class<Self>("User")({
-    //     id: S.BigIntFromSelf,
-    //     role: S.Union(S.Literal("BasicUser"), S.Literal("Admin")),
-    // }),
-    TaggedClass<Self>()("User", {
+    MutableClass<Self>("User")({
         id: S.BigIntFromSelf,
         role: S.Union(S.Literal("BasicUser"), S.Literal("Admin")),
     }),
+    // TaggedClass<Self>()("User", {
+    //     id: S.BigIntFromSelf,
+    //     role: S.Union(S.Literal("BasicUser"), S.Literal("Admin")),
+    // }),
 
     // Mutable,
     MobXObservable,