Index: src/GenPoly/Specialize.cc
===================================================================
--- src/GenPoly/Specialize.cc	(revision b6fd7517dcd49accffbb4e92357f4fec8890b879)
+++ src/GenPoly/Specialize.cc	(revision b3b2077b1feda429f174cfb4f374cb1e00580630)
@@ -147,5 +147,5 @@
 
 	Expression * Specialize::doSpecialization( Type *formalType, Expression *actual, InferredParams *inferParams ) {
-		assert( actual->has_result() );
+		assertf( actual->has_result(), "attempting to specialize an untyped expression" );
 		if ( needsSpecialization( formalType, actual->get_result(), env ) ) {
 			FunctionType *funType;