diff --git a/crdt.cabal b/crdt.cabal
--- a/crdt.cabal
+++ b/crdt.cabal
@@ -1,5 +1,5 @@
 name: crdt
-version: 10.1
+version: 10.2
           -- ^ ComVer
 category: Distributed Systems
 copyright:
@@ -25,7 +25,8 @@
     build-depends:  base >= 4.8 && < 4.12
                   , binary
                   , bytestring
-                  , containers
+                  , containers >= 0.5.9
+                    -- since lookupMax is used
                   , Diff
                   , hashable
                   , mtl