diff --git a/com.epistimis.uddl/src/com/epistimis/uddl/extension/conceptualExtensions.ocl b/com.epistimis.uddl/src/com/epistimis/uddl/extension/conceptualExtensions.ocl
index 2d87ac6..6f3fad4 100644
--- a/com.epistimis.uddl/src/com/epistimis/uddl/extension/conceptualExtensions.ocl
+++ b/com.epistimis.uddl/src/com/epistimis/uddl/extension/conceptualExtensions.ocl
@@ -173,7 +173,7 @@ package uddl
 		 */
 		def: typeReferences(): Set(ConceptualComposableElement) =
 			let myComps = self.composition->collect(type.referencedModelTypes())->flatten()->asSet() in
-			let parentTypes = if (self.specializes.oclIsUndefined()) then  Bag {} 
+			let parentTypes = if (self.specializes.oclIsUndefined()) then  Set {} 
 			else 
 				if self.specializes.oclIsKindOf(ConceptualAssociation) then
 					self.specializes.oclAsType(ConceptualAssociation).referencedModelTypes()