diff --git a/src/effect/EffectSchemaTraitExpressionBuilder.ts b/src/effect/EffectSchemaTraitExpressionBuilder.ts
index 18e6be3..6918b16 100644
--- a/src/effect/EffectSchemaTraitExpressionBuilder.ts
+++ b/src/effect/EffectSchemaTraitExpressionBuilder.ts
@@ -104,7 +104,7 @@ export class EffectSchemaTraitExpressionBuilder<
 
     mutableEncoded() {
         return new EffectSchemaTraitExpressionBuilder(
-            this.expressionSuperclass as S.Class<unknown, Fields, Readonly<I>, R, C, Inherited, Proto>,
+            this.expressionSuperclass as S.Class<unknown, Fields, Types.Mutable<I>, R, C, Inherited, Proto>,
             this.expressionSuperclassStatic,
             this.expressionTraits,
         )
@@ -112,7 +112,7 @@ export class EffectSchemaTraitExpressionBuilder<
 
     immutableEncoded() {
         return new EffectSchemaTraitExpressionBuilder(
-            this.expressionSuperclass as S.Class<unknown, Fields, Types.Mutable<I>, R, C, Inherited, Proto>,
+            this.expressionSuperclass as S.Class<unknown, Fields, Readonly<I>, R, C, Inherited, Proto>,
             this.expressionSuperclassStatic,
             this.expressionTraits,
         )
diff --git a/src/effect/tests.ts b/src/effect/tests.ts
index aa33f91..c51f12f 100644
--- a/src/effect/tests.ts
+++ b/src/effect/tests.ts
@@ -34,7 +34,7 @@ const userExp = effectSchemaExpression
         role:  S.Union(S.Literal("User"), S.Literal("Admin")),
     })
     // .mutable()
-    // .mutableEncoded()
+    .mutableEncoded()
     .build()
 
 @userExp.staticImplements
@@ -43,6 +43,8 @@ export class User extends userExp.extends<User>() implements Implements<typeof u
     static aStaticMethodThatShouldBeInherited() {}
 }
 
+User.Encoded
+
 const user = new User({ id: 0n, role: "User" })
 // user.id = 0n