diff --git a/Python/getargs.c b/Python/getargs.c
index aa4a228..00f298a 100644
--- a/Python/getargs.c
+++ b/Python/getargs.c
@@ -84,6 +84,8 @@
 	int i, len;
 	char *msg;
 	
+	assert(compat || (args != (PyObject*)NULL));
+
 	for (;;) {
 		int c = *format++;
 		if (c == '(' /* ')' */) {