diff --git a/refs.c b/refs.c
index 9d9bbebfb9..6b4236a67f 100644
--- a/refs.c
+++ b/refs.c
@@ -2706,6 +2706,9 @@ static int rename_ref_available(const char *oldname, const char *newname)
 	return ret;
 }
 
+static int write_ref_sha1(struct ref_lock *lock, const unsigned char *sha1,
+			  const char *logmsg);
+
 int rename_ref(const char *oldrefname, const char *newrefname, const char *logmsg)
 {
 	unsigned char sha1[20], orig_sha1[20];
@@ -2950,8 +2953,11 @@ int is_branch(const char *refname)
 	return !strcmp(refname, "HEAD") || starts_with(refname, "refs/heads/");
 }
 
-/* This function must return a meaningful errno */
-int write_ref_sha1(struct ref_lock *lock,
+/*
+ * Write sha1 into the ref specified by the lock. Make sure that errno
+ * is sane on error.
+ */
+static int write_ref_sha1(struct ref_lock *lock,
 	const unsigned char *sha1, const char *logmsg)
 {
 	static char term = '\n';
diff --git a/refs.h b/refs.h
index 50b115acc1..eea104478f 100644
--- a/refs.h
+++ b/refs.h
@@ -197,9 +197,6 @@ extern int commit_ref(struct ref_lock *lock);
 /** Release any lock taken but not written. **/
 extern void unlock_ref(struct ref_lock *lock);
 
-/** Writes sha1 into the ref specified by the lock. **/
-extern int write_ref_sha1(struct ref_lock *lock, const unsigned char *sha1, const char *msg);
-
 /*
  * Setup reflog before using. Set errno to something meaningful on failure.
  */