Index: src/GenPoly/Specialize.cc
===================================================================
--- src/GenPoly/Specialize.cc	(revision e9a3b20b59d320eed25770a9bc1951960a34848a)
+++ src/GenPoly/Specialize.cc	(revision 969ee0df8f39d24fff9d38d5eaf051360168d748)
@@ -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." );