diff --git a/ChangeLog b/ChangeLog
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,6 @@
+2017-10-11  Ferdinand van Walree 0.1.1
+* Fixed Functor definition for STTerm
+
 2017-09-29  Ferdinand van Walree 0.1.0
 
 * Initial release.
diff --git a/sessiontypes.cabal b/sessiontypes.cabal
--- a/sessiontypes.cabal
+++ b/sessiontypes.cabal
@@ -1,5 +1,5 @@
 name:                sessiontypes
-version:             0.1.0
+version:             0.1.1
 synopsis:            Session types library
 description:         This packages provides a deep embedded domain-specific language for writing session typed program.
                      A session typed program is a program annotated with session types. A session type describes a communication protocol at the type-level.
diff --git a/src/Control/SessionTypes/Debug.hs b/src/Control/SessionTypes/Debug.hs
--- a/src/Control/SessionTypes/Debug.hs
+++ b/src/Control/SessionTypes/Debug.hs
@@ -192,7 +192,7 @@
   O_Rec ::       Output ('Cap (s ': ctx) s) b ->        Output ('Cap ctx (R s)) b
   O_Var ::       Output ('Cap (s ': ctx) s) b ->        Output ('Cap (s ': ctx) V) b
   O_Weaken ::    Output ('Cap ctx s) b ->               Output ('Cap (t ': ctx) (Wk s)) b
-  O_Eps :: b ->  Output ('Cap ctx Eps) b
+  O_Eps :: b ->  Output ('Cap '[] Eps) b
   O_Lift ::      Output s b -> Output s b
 
 -- | Extracts all result values from a given `Output`
diff --git a/src/Control/SessionTypes/STTerm.hs b/src/Control/SessionTypes/STTerm.hs
--- a/src/Control/SessionTypes/STTerm.hs
+++ b/src/Control/SessionTypes/STTerm.hs
@@ -110,8 +110,8 @@
   return x = Ret x
   (Ret x) >>= f = f x
 
-instance I.IxFunctor (STTerm m) where
-  fmap f (Send a r) = Send a (I.fmap f r)
+instance Monad m => I.IxFunctor (STTerm m) where
+  fmap f st = st I.>>= \a -> I.return $ f a
 
 instance Monad m => I.IxApplicative (STTerm m) where
   pure x = Ret x
diff --git a/src/Control/SessionTypes/Types.hs b/src/Control/SessionTypes/Types.hs
--- a/src/Control/SessionTypes/Types.hs
+++ b/src/Control/SessionTypes/Types.hs
@@ -134,7 +134,6 @@
   RemoveRecvST (Wk s) = Wk (RemoveRecvST s)
   RemoveRecvST s = s
 
-
 -- | Type family for applying a constraint to types of kind `Type` in a session type. It may be applied to a capability.
 type family HasConstraint (c :: Type -> Constraint) s :: Constraint where
   HasConstraint c ('Cap ctx s) = (HasConstraintST c s, MapHasConstraint c ctx)
diff --git a/test/Test/Debug/Main.hs b/test/Test/Debug/Main.hs
--- a/test/Test/Debug/Main.hs
+++ b/test/Test/Debug/Main.hs
@@ -73,7 +73,3 @@
       s `shouldBe` (O_Rec $ O_Sel1 $ O_Send "text.txt" $ O_Recv (Right "hello") $ O_Var $
                             O_Sel1 $ O_Send "doesnotexist.txt" $ O_Recv (Left "File does not exist") $ O_Lift $ O_Var $
                             O_Sel2 $ O_Sel1 $ O_Weaken $ O_Eps ["hello"])
-  
-  
-
-