diff --git a/commit.h b/commit.h
index f2f39e1a89..e9dee8d26b 100644
--- a/commit.h
+++ b/commit.h
@@ -400,8 +400,6 @@ LAST_ARG_MUST_BE_NULL
 int run_commit_hook(int editor_is_used, const char *index_file,
 		    int *invoked_hook, const char *name, ...);
 
-/* Sign a commit or tag buffer, storing the result in a header. */
-int sign_with_header(struct strbuf *buf, const char *keyid);
 /* Parse the signature out of a header. */
 int parse_buffer_signed_by_header(const char *buffer,
 				  unsigned long size,