Index: src/GenPoly/GenPoly.cc
===================================================================
--- src/GenPoly/GenPoly.cc	(revision c1ec14f5fd75a4980c439c4260b080871fa4c704)
+++ src/GenPoly/GenPoly.cc	(revision 4d6d62ed4859b907bfb967784da082be0112c77a)
@@ -371,4 +371,8 @@
 			return is<VoidType>( ap->get_base() ) || is<VoidType>( bp->get_base() )
 				|| typesPolyCompatible( ap->get_base(), bp->get_base() );
+		} else if ( aid == type_index{typeid(ReferenceType)} ) {
+			ReferenceType *ap = as<ReferenceType>(a), *bp = as<ReferenceType>(b);
+			return is<VoidType>( ap->get_base() ) || is<VoidType>( bp->get_base() )
+				|| typesPolyCompatible( ap->get_base(), bp->get_base() );
 		} else if ( aid == type_index{typeid(ArrayType)} ) {
 			ArrayType *aa = as<ArrayType>(a), *ba = as<ArrayType>(b);