diff --git a/server/src/main/java/org/elasticsearch/index/mapper/IdLoader.java b/server/src/main/java/org/elasticsearch/index/mapper/IdLoader.java
index 2f45d37fed51b..6fc9820a081db 100644
--- a/server/src/main/java/org/elasticsearch/index/mapper/IdLoader.java
+++ b/server/src/main/java/org/elasticsearch/index/mapper/IdLoader.java
@@ -77,8 +77,8 @@ public IdLoader.Leaf leaf(LeafStoredFieldLoader loader, LeafReader reader, int[]
                 int docId = docIdsInLeaf[i];
                 var routingBuilder = builders[i];
 
-                tsIdDocValues.advanceExact(docId);
-                assert tsIdDocValues.getValueCount() == 1;
+                boolean found = tsIdDocValues.advanceExact(docId);
+                assert found;
                 BytesRef tsid = tsIdDocValues.lookupOrd(tsIdDocValues.ordValue());
                 timestampDocValues.advanceExact(docId);
                 assert timestampDocValues.docValueCount() == 1;