diff --git a/src/effect/schema/class/Mutable.ts b/src/effect/schema/class/Mutable.ts
index d041490..566a16f 100644
--- a/src/effect/schema/class/Mutable.ts
+++ b/src/effect/schema/class/Mutable.ts
@@ -1,48 +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 { Class, Struct } from "@effect/schema/Schema"
 import type { Constructor } from "type-fest"
 import type { StaticType } from "../../.."
-import type { HasFields, MissingSelfGeneric } from "./util"
-
-
-export type TMutableClass<
-    Self,
-    Fields extends Struct.Fields,
-    I, R, C,
-    Inherited,
-    Proto,
-> = (
-    Constructor<
-        Omit<
-            InstanceType<Class<Self, Fields, I, R, C, Inherited, Proto>>,
-            keyof Fields
-        > &
-        Mutable<Struct.Type<Fields>>,
-
-        ConstructorParameters<Class<Self, Fields, I, R, C, Inherited, Proto>>
-    > &
-
-    Omit<
-        StaticType<Class<Self, Fields, I, R, C, Inherited, Proto>>,
-        "extend"
-    > & {
-        extend<Extended = never>(identifier: string): <newFields extends Struct.Fields>(
-            fields:        newFields | HasFields<newFields>,
-            annotations?:  Annotations.Schema<Extended>,
-        ) => [Extended] extends [never]
-            ? MissingSelfGeneric<"Base.extend">
-            : TMutableClass<
-                Extended,
-                Fields & newFields,
-                I & Struct.Encoded<newFields>,
-                R | Struct.Context<newFields>,
-                C & Struct.Constructor<newFields>,
-                Self,
-                Proto
-            >
-    }
-)
+import type { TMutableClass } from "./TMutableClass"
 
 
 export function Mutable<
@@ -58,5 +17,21 @@ export function Mutable<
         | This
         | Class<Self, Fields, I, R, C, Inherited, Proto>
 ) {
+    return class_ as (
+        Constructor<
+            Omit<
+                InstanceType<This>,
+                keyof InstanceType<TMutableClass<Self, Fields, I, R, C, Inherited, Proto>>
+            > &
+            InstanceType<TMutableClass<Self, Fields, I, R, C, Inherited, Proto>>,
 
+            ConstructorParameters<TMutableClass<Self, Fields, I, R, C, Inherited, Proto>>
+        > &
+
+        Omit<
+            StaticType<This>,
+            keyof StaticType<TMutableClass<Self, Fields, I, R, C, Inherited, Proto>>
+        > &
+        StaticType<TMutableClass<Self, Fields, I, R, C, Inherited, Proto>>
+    )
 }
diff --git a/src/effect/schema/class/MutableClass.ts b/src/effect/schema/class/MutableClass.ts
index 91af1ba..dfb3861 100644
--- a/src/effect/schema/class/MutableClass.ts
+++ b/src/effect/schema/class/MutableClass.ts
@@ -1,49 +1,9 @@
 import { Schema as S } from "@effect/schema"
-import type { Annotations, Class, Struct } from "@effect/schema/Schema"
-import type { Mutable } from "effect/Types"
-import type { Constructor } from "type-fest"
-import type { StaticType } from "../../.."
+import type { Annotations, Struct } from "@effect/schema/Schema"
+import type { TMutableClass } from "./TMutableClass"
 import type { HasFields, MissingSelfGeneric } from "./util"
 
 
-export type TMutableClass<
-    Self,
-    Fields extends Struct.Fields,
-    I, R, C,
-    Inherited,
-    Proto,
-> = (
-    Constructor<
-        Omit<
-            InstanceType<Class<Self, Fields, I, R, C, Inherited, Proto>>,
-            keyof Fields
-        > &
-        Mutable<Struct.Type<Fields>>,
-
-        ConstructorParameters<Class<Self, Fields, I, R, C, Inherited, Proto>>
-    > &
-
-    Omit<
-        StaticType<Class<Self, Fields, I, R, C, Inherited, Proto>>,
-        "extend"
-    > & {
-        extend<Extended = never>(identifier: string): <newFields extends Struct.Fields>(
-            fields:        newFields | HasFields<newFields>,
-            annotations?:  Annotations.Schema<Extended>,
-        ) => [Extended] extends [never]
-            ? MissingSelfGeneric<"Base.extend">
-            : TMutableClass<
-                Extended,
-                Fields & newFields,
-                I & Struct.Encoded<newFields>,
-                R | Struct.Context<newFields>,
-                C & Struct.Constructor<newFields>,
-                Self,
-                Proto
-            >
-    }
-)
-
 export const MutableClass = <Self = never>(identifier: string) => (
     <Fields extends Struct.Fields>(
         fieldsOr:      Fields | HasFields<Fields>,
diff --git a/src/effect/schema/class/TMutableClass.ts b/src/effect/schema/class/TMutableClass.ts
new file mode 100644
index 0000000..8b4a183
--- /dev/null
+++ b/src/effect/schema/class/TMutableClass.ts
@@ -0,0 +1,44 @@
+import type { Annotations, Class, Struct } from "@effect/schema/Schema"
+import type { Mutable } from "effect/Types"
+import type { Constructor } from "type-fest"
+import type { StaticType } from "../../.."
+import type { HasFields, MissingSelfGeneric } from "./util"
+
+
+export type TMutableClass<
+    Self,
+    Fields extends Struct.Fields,
+    I, R, C,
+    Inherited,
+    Proto,
+> = (
+    Constructor<
+        Omit<
+            InstanceType<Class<Self, Fields, I, R, C, Inherited, Proto>>,
+            keyof Fields
+        > &
+        Mutable<Struct.Type<Fields>>,
+
+        ConstructorParameters<Class<Self, Fields, I, R, C, Inherited, Proto>>
+    > &
+
+    Omit<
+        StaticType<Class<Self, Fields, I, R, C, Inherited, Proto>>,
+        "extend"
+    > & {
+        extend<Extended = never>(identifier: string): <newFields extends Struct.Fields>(
+            fields:        newFields | HasFields<newFields>,
+            annotations?:  Annotations.Schema<Extended>,
+        ) => [Extended] extends [never]
+            ? MissingSelfGeneric<"Base.extend">
+            : TMutableClass<
+                Extended,
+                Fields & newFields,
+                I & Struct.Encoded<newFields>,
+                R | Struct.Context<newFields>,
+                C & Struct.Constructor<newFields>,
+                Self,
+                Proto
+            >
+    }
+)
diff --git a/src/effect/schema/class/index.ts b/src/effect/schema/class/index.ts
index 391c95d..48c560e 100644
--- a/src/effect/schema/class/index.ts
+++ b/src/effect/schema/class/index.ts
@@ -1,3 +1,4 @@
 export { MobXObservable } from "./MobXObservable"
+export { Mutable } from "./Mutable"
 export { MutableClass } from "./MutableClass"
-export type { TMutableClass } from "./MutableClass"
+export type { TMutableClass } from "./TMutableClass"