Index: src/GenPoly/InstantiateGeneric.cc
===================================================================
--- src/GenPoly/InstantiateGeneric.cc	(revision dd0c97ba0a6e76dbcf399c982e690763d09792f5)
+++ src/GenPoly/InstantiateGeneric.cc	(revision 4d3cba5018d14662f3a3e2b163c7ba33285e3b39)
@@ -152,4 +152,5 @@
 	class EnvFinder final : public GenPoly::PolyMutator {
 	public:
+		using GenPoly::PolyMutator::mutate;
 		virtual Type * mutate( TypeInstType * inst ) override {
 			if ( env ) envMap[inst] = env;