diff --git a/src/proto/sha256.pro b/src/proto/sha256.pro
index e9a3d3c..c5237f4 100644
--- a/src/proto/sha256.pro
+++ b/src/proto/sha256.pro
@@ -1,6 +1,6 @@
 /* sha256.c */
 void sha256_start __ARGS((context_sha256_T *ctx));
-void sha256_update __ARGS((context_sha256_T *ctx, char_u *input, uint32_t length));
+void sha256_update __ARGS((context_sha256_T *ctx, char_u *input, UINT32_T length));
 void sha256_finish __ARGS((context_sha256_T *ctx, char_u digest[32]));
 char_u *sha256_key __ARGS((char_u *buf));
 int sha256_self_test __ARGS((void));