diff --git a/src/TraitExpression.ts b/src/TraitExpression.ts
index 179839a..ade1782 100644
--- a/src/TraitExpression.ts
+++ b/src/TraitExpression.ts
@@ -15,11 +15,12 @@ export class TraitExpression<
 
     get extends(): (
         AbstractClass<
+            InstanceType<Superclass> &  // Keep the instance of the superclass outside of any kind of type manipulation
+                                        // as it can accidentely remove abstract properties
             Simplify<
-                Extend<[
-                    InstanceType<Superclass>,
-                    ...TraitTuple.MapImplInstance<Traits>,
-                ]>
+                Extend<
+                    TraitTuple.MapImplInstance<Traits>
+                >
             >,
 
             ConstructorParameters<Superclass>
@@ -140,11 +141,12 @@ export type TraitExpressionConcreteClass<
 export type TraitExpressionInstance<
     Exp extends TraitExpression<any, Trait<any, any, any, any>[]>
 > = (
+    InstanceType<TraitExpression.Superclass<Exp>> &  // Keep the instance of the superclass outside of any kind of type manipulation
+                                                     // as it can accidentely remove abstract properties
     Simplify<
-        Extend<[
-            InstanceType<TraitExpression.Superclass<Exp>>,
-            ...TraitTuple.MapInstance<TraitExpression.Traits<Exp>>,
-        ]>
+        Extend<
+            TraitTuple.MapInstance<TraitExpression.Traits<Exp>>
+        >
     >
 )
 
diff --git a/src/tests.ts b/src/tests.ts
index b7ada34..3725da4 100644
--- a/src/tests.ts
+++ b/src/tests.ts
@@ -1,4 +1,4 @@
-import { Simplify } from "type-fest"
+import { AbstractClass, Simplify } from "type-fest"
 import { TraitClass } from "./Trait"
 import { trait } from "./TraitBuilder"
 import { Implements, ImplementsStatic, TraitExpressionClass } from "./TraitExpression"
@@ -85,7 +85,17 @@ class User extends exp.extends implements Implements<typeof exp> {
 console.log(new User())
 
 
-type T = NonExtendableKeys<[
-    { prout: "gneugneu" },
-    { prout: string },
-]>
+abstract class Test {
+    abstract prout: string
+}
+
+const MappedTest = Test as AbstractClass<Test>
+
+class ConcreteTest extends MappedTest {
+
+}
+
+// type T = NonExtendableKeys<[
+//     { prout: "gneugneu" },
+//     { prout: string },
+// ]>