diff --git a/lucene/grouping/src/test/org/apache/lucene/search/grouping/GroupingSearchTest.java b/lucene/grouping/src/test/org/apache/lucene/search/grouping/GroupingSearchTest.java
index d13bfd73e4b..d09513ca128 100644
--- a/lucene/grouping/src/test/org/apache/lucene/search/grouping/GroupingSearchTest.java
+++ b/lucene/grouping/src/test/org/apache/lucene/search/grouping/GroupingSearchTest.java
@@ -31,6 +31,7 @@ import org.apache.lucene.search.IndexSearcher;
 import org.apache.lucene.search.Query;
 import org.apache.lucene.search.Sort;
 import org.apache.lucene.search.TermQuery;
+import org.apache.lucene.search.similarities.BM25Similarity;
 import org.apache.lucene.store.Directory;
 import org.apache.lucene.util.BytesRef;
 import org.apache.lucene.util.LuceneTestCase;
@@ -115,6 +116,7 @@ public class GroupingSearchTest extends LuceneTestCase {
     w.addDocument(doc);
 
     IndexSearcher indexSearcher = newSearcher(w.getReader());
+    indexSearcher.setSimilarity(new BM25Similarity());
     w.close();
 
     Sort groupSort = Sort.RELEVANCE;