--- a/ed2k_hash/md4.h
+++ b/ed2k_hash/md4.h
@@ -66,7 +66,8 @@
 typedef unsigned short int UINT2;
 
 /* UINT4 defines a four byte word */
-typedef unsigned long int UINT4;
+/* unsigned long int on 64bit is 8 bits */
+typedef unsigned int UINT4;
 
 /* PROTO_LIST is defined depending on how PROTOTYPES is defined above.
    If using PROTOTYPES, then PROTO_LIST returns the list, otherwise it