diff --git a/src/core/thread/mle_router.cpp b/src/core/thread/mle_router.cpp
index 12188b156..bdd3da41f 100644
--- a/src/core/thread/mle_router.cpp
+++ b/src/core/thread/mle_router.cpp
@@ -2724,7 +2724,7 @@ otError MleRouter::SendChildIdResponse(Child *aChild)
     SuccessOrExit(error = AppendActiveTimestamp(*message));
     SuccessOrExit(error = AppendPendingTimestamp(*message));
 
-    if (aChild->GetState() != Neighbor::kStateValid)
+    if (aChild->GetRloc16() == 0)
     {
         // pick next Child ID that is not being used
         do