diff --git a/Annotations.cabal b/Annotations.cabal
--- a/Annotations.cabal
+++ b/Annotations.cabal
@@ -1,5 +1,5 @@
 Name:           Annotations
-Version:        0.1.1
+Version:        0.1.2
 Synopsis:       Constructing, analyzing and destructing annotated trees
 Description:
   @Annotations@ provides utility functions to make working with annotated trees easier. There are two implementations: one for working with open datatypes that explicitly make their child positions accessible through a type argument, and one for working with MultiRec datatypes.
@@ -19,8 +19,8 @@
 Build-type:     Simple
 
 Library
-  Build-Depends:    base >= 4.1 && < 4.3, mtl >= 1.1 && < 1.2,
-                    parsec >= 3.0 && < 3.1, multirec >= 0.4 && < 0.5
+  Build-Depends:    base >= 4.1 && < 4.4, mtl >= 1.1 && < 2.1,
+                    parsec >= 3.0 && < 3.2, multirec >= 0.4 && < 0.5
   Exposed-Modules:  Annotations.Bounds,
                     Annotations.BoundsParser,
                     Annotations.Except,
diff --git a/Annotations/MultiRec/ErrorAlg.hs b/Annotations/MultiRec/ErrorAlg.hs
--- a/Annotations/MultiRec/ErrorAlg.hs
+++ b/Annotations/MultiRec/ErrorAlg.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE GADTs                 #-}
 {-# LANGUAGE TypeFamilies          #-}
 {-# LANGUAGE TypeOperators         #-}
 {-# LANGUAGE Rank2Types            #-}
diff --git a/Annotations/MultiRec/Yield.hs b/Annotations/MultiRec/Yield.hs
--- a/Annotations/MultiRec/Yield.hs
+++ b/Annotations/MultiRec/Yield.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE GADTs #-}
 {-# LANGUAGE TypeFamilies #-}
 {-# LANGUAGE KindSignatures #-}
 {-# LANGUAGE FlexibleContexts #-}
diff --git a/Annotations/MultiRec/ZipperFix.hs b/Annotations/MultiRec/ZipperFix.hs
--- a/Annotations/MultiRec/ZipperFix.hs
+++ b/Annotations/MultiRec/ZipperFix.hs
@@ -1,4 +1,5 @@
 {-# LANGUAGE RankNTypes #-}
+{-# LANGUAGE GADTs #-}
 
 -- | Zipper functions specialised to work on fixpoints of pattern functors.
 module Annotations.MultiRec.ZipperFix (