diff --git a/src/proto/sha256.pro b/src/proto/sha256.pro
index a6d6be7..e9a3d3c 100644
--- a/src/proto/sha256.pro
+++ b/src/proto/sha256.pro
@@ -1,4 +1,7 @@
 /* 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_finish __ARGS((context_sha256_T *ctx, char_u digest[32]));
 char_u *sha256_key __ARGS((char_u *buf));
 int sha256_self_test __ARGS((void));
 void sha2_seed __ARGS((char_u header[], int header_len));