diff --git a/Data/IntMultiSet.hs b/Data/IntMultiSet.hs
index 31cf684..25f649b 100644
--- a/Data/IntMultiSet.hs
+++ b/Data/IntMultiSet.hs
@@ -562,17 +562,17 @@ toAscOccurList = Map.toAscList . unMS
 
 -- | /O(n*min(n,W))/. Create a multiset from a list of element\/occurence pairs.
 fromOccurList :: [(Int,Int)] -> IntMultiSet 
-fromOccurList = MS . Map.fromListWith (+)
+fromOccurList = MS . Map.filter (>0) . Map.fromListWith (+)
 
 -- | /O(n)/. Build a multiset from an ascending list of element\/occurence pairs in linear time.
 -- /The precondition (input list is ascending) is not checked./
 fromAscOccurList :: [(Int,Int)] -> IntMultiSet 
-fromAscOccurList = MS . Map.fromAscListWith (+)
+fromAscOccurList = MS . Map.filter (>0) . Map.fromAscListWith (+)
 
 -- | /O(n)/. Build a multiset from an ascending list of elements\/occurence pairs where each elements appears only once.
 -- /The precondition (input list is strictly ascending) is not checked./
 fromDistinctAscOccurList :: [(Int,Int)] -> IntMultiSet 
-fromDistinctAscOccurList = MS . Map.fromDistinctAscList
+fromDistinctAscOccurList = MS . Map.filter (>0) . Map.fromDistinctAscList
 
 {--------------------------------------------------------------------
   Map
diff --git a/Data/MultiSet.hs b/Data/MultiSet.hs
index 79fa726..315266f 100644
--- a/Data/MultiSet.hs
+++ b/Data/MultiSet.hs
@@ -556,17 +556,17 @@ toAscOccurList = Map.toAscList . unMS
 
 -- | /O(n*log n)/. Create a multiset from a list of element\/occurence pairs.
 fromOccurList :: Ord a => [(a,Occur)] -> MultiSet a 
-fromOccurList = MS . Map.fromListWith (+)
+fromOccurList = MS . Map.filter (>0) . Map.fromListWith (+)
 
 -- | /O(n)/. Build a multiset from an ascending list of element\/occurence pairs in linear time.
 -- /The precondition (input list is ascending) is not checked./
 fromAscOccurList :: Eq a => [(a,Occur)] -> MultiSet a 
-fromAscOccurList = MS . Map.fromAscListWith (+)
+fromAscOccurList = MS . Map.filter (>0) . Map.fromAscListWith (+)
 
 -- | /O(n)/. Build a multiset from an ascending list of elements\/occurence pairs where each elements appears only once.
 -- /The precondition (input list is strictly ascending) is not checked./
 fromDistinctAscOccurList :: [(a,Occur)] -> MultiSet a 
-fromDistinctAscOccurList = MS . Map.fromDistinctAscList
+fromDistinctAscOccurList = MS . Map.filter (>0) . Map.fromDistinctAscList
 
 {--------------------------------------------------------------------
   Map