diff --git a/src/backend/replication/syncrep.c b/src/backend/replication/syncrep.c
index be5f055d8ec..f6c3538650d 100644
--- a/src/backend/replication/syncrep.c
+++ b/src/backend/replication/syncrep.c
@@ -71,7 +71,9 @@ static bool announce_next_takeover = true;
 static void SyncRepQueueInsert(void);
 
 static int SyncRepGetStandbyPriority(void);
+#ifdef USE_ASSERT_CHECKING
 static bool SyncRepQueueIsOrderedByLSN(void);
+#endif
 
 /*
  * ===========================================================