diff --git a/monoidal-containers.cabal b/monoidal-containers.cabal
--- a/monoidal-containers.cabal
+++ b/monoidal-containers.cabal
@@ -1,5 +1,5 @@
 name:                monoidal-containers
-version:             0.1.1.0
+version:             0.1.2.0
 synopsis:            Containers with monoidal accumulation
 description:         Containers with monoidal accumulation
 homepage:            http://github.com/bgamari/monoidal-containers
diff --git a/src/Data/Map/Monoidal.hs b/src/Data/Map/Monoidal.hs
--- a/src/Data/Map/Monoidal.hs
+++ b/src/Data/Map/Monoidal.hs
@@ -101,9 +101,9 @@
     {-# INLINE unpack #-}
 
 #if MIN_VERSION_base(4,7,0)
-instance Ord k => IsList (MonoidalMap k a) where
+instance (Ord k, Monoid a) => IsList (MonoidalMap k a) where
     type Item (MonoidalMap k a) = (k, a)
-    fromList = MM . M.fromList
+    fromList = MM . M.fromListWith mappend
     {-# INLINE fromList #-}
     toList = M.toList . unpack
     {-# INLINE toList #-}