diff --git a/CHANGELOG b/CHANGELOG
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,3 +1,6 @@
+0.3.4.1 (2018-09-23)
+ * Add support for containers-0.6.0.1 (shipped with GHC 8.6.1)
+
 0.3.4 (2018-05-28)
  * #29: Add Semigroup instances (needed for GHC 8.4)
  * Add NfData instances
diff --git a/Data/IntMultiSet.hs b/Data/IntMultiSet.hs
--- a/Data/IntMultiSet.hs
+++ b/Data/IntMultiSet.hs
@@ -145,7 +145,12 @@
 import Data.IntMap.Strict (IntMap)
 import Data.IntSet (IntSet)
 import Data.MultiSet (MultiSet)
+#if MIN_VERSION_containers(0,5,11)
+import qualified Data.IntMap.Strict as Map hiding (showTreeWith)
+import qualified Data.IntMap.Internal.Debug as Map (showTreeWith)
+#else
 import qualified Data.IntMap.Strict as Map
+#endif
 import qualified Data.IntSet as Set
 import qualified Data.List as List
 import qualified Data.MultiSet as MultiSet
@@ -461,8 +466,7 @@
 -- TODO: IntMap doesn't have a mapKeys function
 map f = fromOccurList . List.map (\(x,o) -> (f x, o)) . toOccurList
 
--- | /O(n)/. The 
---
+-- | /O(n)/.
 -- @'mapMonotonic' f s == 'map' f s@, but works only when @f@ is strictly monotonic.
 -- /The precondition is not checked./
 -- Semi-formally, we have:
diff --git a/Data/MultiSet.hs b/Data/MultiSet.hs
--- a/Data/MultiSet.hs
+++ b/Data/MultiSet.hs
@@ -151,7 +151,12 @@
 import qualified Data.Foldable as Foldable
 import Data.Map.Strict (Map)
 import Data.Set (Set)
+#if MIN_VERSION_containers(0,5,11)
+import qualified Data.Map.Strict as Map hiding (showTreeWith)
+import qualified Data.Map.Internal.Debug as Map (showTreeWith)
+#else
 import qualified Data.Map.Strict as Map
+#endif
 import qualified Data.Set as Set
 import qualified Data.List as List
 import Control.DeepSeq (NFData(..))
@@ -452,8 +457,7 @@
 map :: (Ord b) => (a->b) -> MultiSet a -> MultiSet b
 map f = MS . Map.mapKeysWith (+) f . unMS
 
--- | /O(n)/. The 
---
+-- | /O(n)/.
 -- @'mapMonotonic' f s == 'map' f s@, but works only when @f@ is strictly monotonic.
 -- /The precondition is not checked./
 -- Semi-formally, we have:
diff --git a/multiset.cabal b/multiset.cabal
--- a/multiset.cabal
+++ b/multiset.cabal
@@ -1,5 +1,5 @@
 name:             multiset
-version:          0.3.4
+version:          0.3.4.1
 author:           Twan van Laarhoven
 maintainer:       twanvl@gmail.com
 bug-reports:      https://github.com/twanvl/multiset/issues