diff --git a/server/src/main/java/org/elasticsearch/index/engine/LuceneChangesSnapshot.java b/server/src/main/java/org/elasticsearch/index/engine/LuceneChangesSnapshot.java
index d8881cbad9944..d4466cbc17c54 100644
--- a/server/src/main/java/org/elasticsearch/index/engine/LuceneChangesSnapshot.java
+++ b/server/src/main/java/org/elasticsearch/index/engine/LuceneChangesSnapshot.java
@@ -16,6 +16,7 @@
 import org.apache.lucene.util.ArrayUtil;
 import org.elasticsearch.common.bytes.BytesReference;
 import org.elasticsearch.common.lucene.index.SequentialStoredFieldsLeafReader;
+import org.elasticsearch.core.Assertions;
 import org.elasticsearch.index.IndexVersion;
 import org.elasticsearch.index.fieldvisitor.FieldsVisitor;
 import org.elasticsearch.index.mapper.SourceFieldMapper;