Index: src/GenPoly/Specialize.cc
===================================================================
--- src/GenPoly/Specialize.cc	(revision d56e5bcda08aa6816d20a750cfe4087387b7681f)
+++ src/GenPoly/Specialize.cc	(revision 9c90718da710f56ac37d4c6774e2c2db7b408183)
@@ -99,4 +99,6 @@
 		if ( FunctionType * fftype = getFunctionType( formalType ) ) {
 			if ( fftype->isTtype() ) return true;
+			// conversion of 0 (null) to function type does not require tuple specialization
+			if ( dynamic_cast< ZeroType * >( actualType ) ) return false;
 			FunctionType * aftype = getFunctionType( actualType );
 			assertf( aftype, "formal type is a function type, but actual type is not." );