diff --git a/Foundation/_CPCollectionKVCOperators.j b/Foundation/_CPCollectionKVCOperators.j
index fb9ce1437..6180c29f7 100644
--- a/Foundation/_CPCollectionKVCOperators.j
+++ b/Foundation/_CPCollectionKVCOperators.j
@@ -198,7 +198,7 @@ var _CPCollectionKVCOperatorSimpleRE = /^@(avg|count|m(ax|in)|sum|unionOfObjects
 + (CPArray)distinctUnionOfSetsForCollection:(id)aCollection propertyPath:(CPString)propertyPath
 {
     if (!propertyPath)
-        return [aCollection valueForUndefinedKey:@"@distinctUnionOfArrays"];
+        return [aCollection valueForUndefinedKey:@"@distinctUnionOfSets"];
 
     var objects = [CPMutableSet new],
         number = [aCollection count],