diff --git a/src/sha1.h b/src/sha1.h
index bdba4e8..b5c4ea4 100644
--- a/src/sha1.h
+++ b/src/sha1.h
@@ -52,6 +52,6 @@ typedef struct {
 
 void sha1_init(sha1_ctx_t *);
 void sha1_update(sha1_ctx_t *, const uint8_t *, unsigned int);
-void sha1_final(sha1_ctx_t *, uint8_t *);
+void sha1_final(sha1_ctx_t *, uint8_t[SHA1_DIGESTLEN]);
 void sha1_digest(const char *, char *);
 void sha1_stream(FILE *, char *);