diff --git a/src/effect/schema/MutableClass.ts b/src/effect/schema/MutableClass.ts
index 4c092b6..375be28 100644
--- a/src/effect/schema/MutableClass.ts
+++ b/src/effect/schema/MutableClass.ts
@@ -14,9 +14,11 @@ type TMutableClass<
     Proto,
 > = (
     Constructor<
-        Mutable<Struct.Type<Fields>> &
-        Omit<Inherited, keyof Fields>
-        & Proto,
+        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>>
     > &