Index: src/GenPoly/InstantiateGeneric.cc
===================================================================
--- src/GenPoly/InstantiateGeneric.cc	(revision 2162c2c9192e4775f713c9a98904d0a0f866d966)
+++ src/GenPoly/InstantiateGeneric.cc	(revision 075734f14acde30eb96b3d4a867306b8dcec0eb3)
@@ -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;