diff --git a/Modules/binascii.c b/Modules/binascii.c
index 00f950d..659e08c 100644
--- a/Modules/binascii.c
+++ b/Modules/binascii.c
@@ -874,7 +874,7 @@
 	Py_ssize_t len;
 	long result;
 
-	if ( !PyArg_ParseTuple(args, "s#|l:crc32", &bin_data, &len, &crc) )
+	if ( !PyArg_ParseTuple(args, "s#|k:crc32", &bin_data, &len, &crc) )
 		return NULL;
 
 	crc = ~ crc;