diff --git a/src/hash/crc16.h b/src/hash/crc16.h
index 46e3a7aa54dca67446319756e9b34f3608de28ef..364599cffcfd77a128e16df250018475fbad48bf 100644
--- a/src/hash/crc16.h
+++ b/src/hash/crc16.h
@@ -46,7 +46,7 @@ extern "C" {
 
 extern uint16_t crc16tbl[];
 
-uint16_t crc16(char *data, uint32_t len);
+uint16_t crc16(char* data, unsigned long len);
 
 #ifdef __cplusplus
 }