Index: src/GenPoly/GenPoly.cc
===================================================================
--- src/GenPoly/GenPoly.cc	(revision bfd0a1a522c2b295fec6877eb130540124b1d426)
+++ src/GenPoly/GenPoly.cc	(revision 682dcae3ba54d09eec8ad00203e59ee89c718ea9)
@@ -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);