diff --git a/Data/IntervalMap/FingerTree.hs b/Data/IntervalMap/FingerTree.hs
--- a/Data/IntervalMap/FingerTree.hs
+++ b/Data/IntervalMap/FingerTree.hs
@@ -128,7 +128,7 @@
 instance Foldable (IntervalMap v) where
     foldMap f (IntervalMap t) = foldMap (foldMap f) t
 #if MIN_VERSION_base(4,8,0)
-    null (IntervalMap t) = Prelude.null t
+    null (IntervalMap t) = FT.null t
 #endif
 
 -- | Traverse the intervals in lexicographical order.
@@ -145,7 +145,7 @@
 
 instance (Show v, Show a) => Show (IntervalMap v a) where
     showsPrec p (IntervalMap ns)
-      | Prelude.null ns = showString "empty"
+      | FT.null ns = showString "empty"
       | otherwise =
         showParen (p > 0) (showIntervals (toList ns))
       where
diff --git a/Data/PriorityQueue/FingerTree.hs b/Data/PriorityQueue/FingerTree.hs
--- a/Data/PriorityQueue/FingerTree.hs
+++ b/Data/PriorityQueue/FingerTree.hs
@@ -113,7 +113,7 @@
         Nothing -> mempty
         Just (v, q') -> f v `mappend` foldMap f q'
 #if MIN_VERSION_base(4,8,0)
-    null (PQueue q) = Prelude.null q
+    null (PQueue q) = FT.null q
 #endif
 
 #if MIN_VERSION_base(4,9,0)
@@ -210,7 +210,7 @@
 --
 minViewWithKey :: Ord k => PQueue k v -> Maybe ((k, v), PQueue k v)
 minViewWithKey (PQueue q)
-  | Prelude.null q = Nothing
+  | FT.null q = Nothing
   | otherwise = Just ((k, v), case FT.viewl r of
     _ :< r' -> PQueue (l >< r')
     _ -> error "can't happen")
diff --git a/changelog b/changelog
--- a/changelog
+++ b/changelog
@@ -1,5 +1,8 @@
 -*-change-log-*-
 
+0.1.2.1 Ross Paterson <R.Paterson@city.ac.uk> Oct 2017
+	* Fix for GHC <= 7.8
+
 0.1.2.0 Ross Paterson <R.Paterson@city.ac.uk> Oct 2017
 	* Removed constraint on the type of null
 	* Added versions of fmap and traverse passing the measures of both sides
diff --git a/fingertree.cabal b/fingertree.cabal
--- a/fingertree.cabal
+++ b/fingertree.cabal
@@ -1,5 +1,5 @@
 Name:           fingertree
-Version:        0.1.2.0
+Version:        0.1.2.1
 Cabal-Version:  >= 1.18
 Copyright:      (c) 2006 Ross Paterson, Ralf Hinze
 License:        BSD3