diff --git a/src/IL/Typing.hs b/src/IL/Typing.hs
index 3e3233096cee690aac01d3526afa974ff7837d64..9208275caf04919cee3d08386ca488e80fa5f46d 100644
--- a/src/IL/Typing.hs
+++ b/src/IL/Typing.hs
@@ -11,12 +11,23 @@
    TODO
 -}
 
-module IL.Typing (Typeable(..)) where
+module IL.Typing (Typeable(..), prenexType) where
 
 import Base.Messages (internalError)
 
 import IL.Type
 
+-- | Converts the given type into prenex form.
+prenexType :: Type -> Type
+prenexType (TypeConstructor tc tys) = TypeConstructor tc $ map prenexType tys
+prenexType tv@(TypeVariable _)      = tv
+prenexType (TypeArrow ty1 ty2)      = case prenexType ty2 of
+  TypeForall tvs ty2' -> TypeForall tvs $ TypeArrow (prenexType ty1) ty2'
+  ty2'                -> TypeArrow (prenexType ty1) ty2'
+prenexType (TypeForall tvs ty)      = case prenexType ty of
+  TypeForall tvs' ty' -> TypeForall (tvs ++ tvs') ty'
+  ty'                 -> TypeForall tvs ty'
+
 class Typeable a where
   typeOf :: a -> Type
 
diff --git a/src/Transformations/CurryToIL.hs b/src/Transformations/CurryToIL.hs
index d401933d4de00d499679b46cafdf3da2d394c1a3..67794cb234f8bbee3fe4492577e7377e961564cd 100644
--- a/src/Transformations/CurryToIL.hs
+++ b/src/Transformations/CurryToIL.hs
@@ -213,7 +213,7 @@ trExternal (Var ty f) = do
 -- type constructors.
 
 transType :: TCEnv -> Type -> IL.Type
-transType tcEnv ty' = transType' ty' []
+transType tcEnv ty' = IL.prenexType $ transType' ty' []
   where
     ks = transTVars tcEnv ty'
     transType' (TypeConstructor    tc) = IL.TypeConstructor tc