diff --git a/indexation.cabal b/indexation.cabal
--- a/indexation.cabal
+++ b/indexation.cabal
@@ -1,5 +1,5 @@
 name: indexation
-version: 0.4.5
+version: 0.4.6
 category: Data
 synopsis: Tools for entity indexation
 description: A set of tools for indexing entities
diff --git a/library/Indexation/Functions.hs b/library/Indexation/Functions.hs
--- a/library/Indexation/Functions.hs
+++ b/library/Indexation/Functions.hs
@@ -25,3 +25,6 @@
 
 lookupInIndexSet :: Index entity -> IndexSet entity -> Bool
 lookupInIndexSet (Index indexInt) (IndexSet vec) = vec UnboxedVector.!? indexInt & fromMaybe False
+
+mergeIndexSets :: IndexSet entity -> IndexSet entity -> IndexSet entity
+mergeIndexSets (IndexSet vec1) (IndexSet vec2) = IndexSet $ UnboxedVector.zipWith (||) vec1 vec2