Index: src/SymTab/Validate.cc
===================================================================
--- src/SymTab/Validate.cc	(revision 33218c6845f9825be5a63043ef89bb8a0a80d009)
+++ src/SymTab/Validate.cc	(revision 5ea26ed2fcd7204d100fb83710fcb611e2948b38)
@@ -903,5 +903,5 @@
 		FunctionType * ftype = functionDecl->get_functionType();
 		std::list< DeclarationWithType * > & retVals = ftype->get_returnVals();
-		assertf( retVals.size() == 0 || retVals.size() == 1, "Function %s has too many return values: %d", functionDecl->get_name().c_str(), retVals.size() );
+		assertf( retVals.size() == 0 || retVals.size() == 1, "Function %s has too many return values: %zu", functionDecl->get_name().c_str(), retVals.size() );
 		if ( retVals.size() == 1 ) {
 			// ensure all function return values have a name - use the name of the function to disambiguate (this also provides a nice bit of help for debugging).