diff --git a/refs.c b/refs.c
index c30f4c36be..36439fdb54 100644
--- a/refs.c
+++ b/refs.c
@@ -1396,9 +1396,12 @@ const char *refs_resolve_ref_unsafe(struct ref_store *refs,
 				    unsigned char *sha1, int *flags)
 {
 	static struct strbuf sb_refname = STRBUF_INIT;
+	struct object_id unused_oid;
 	int unused_flags;
 	int symref_count;
 
+	if (!sha1)
+		sha1 = unused_oid.hash;
 	if (!flags)
 		flags = &unused_flags;
 
diff --git a/refs.h b/refs.h
index 78a26400b6..996d4ea54d 100644
--- a/refs.h
+++ b/refs.h
@@ -10,10 +10,11 @@ struct worktree;
 /*
  * Resolve a reference, recursively following symbolic refererences.
  *
- * Store the referred-to object's name in sha1 and return the name of
- * the non-symbolic reference that ultimately pointed at it.  The
- * return value, if not NULL, is a pointer into either a static buffer
- * or the input ref.
+ * Return the name of the non-symbolic reference that ultimately pointed
+ * at the resolved object name.  The return value, if not NULL, is a
+ * pointer into either a static buffer or the input ref.
+ *
+ * If sha1 is non-NULL, store the referred-to object's name in it.
  *
  * If the reference cannot be resolved to an object, the behavior
  * depends on the RESOLVE_REF_READING flag: