diff --git a/lucene/facet/src/test/org/apache/lucene/facet/TestRandomSamplingFacetsCollector.java b/lucene/facet/src/test/org/apache/lucene/facet/TestRandomSamplingFacetsCollector.java
index 5be46bbdd14..cf9d316782a 100644
--- a/lucene/facet/src/test/org/apache/lucene/facet/TestRandomSamplingFacetsCollector.java
+++ b/lucene/facet/src/test/org/apache/lucene/facet/TestRandomSamplingFacetsCollector.java
@@ -68,6 +68,7 @@ public class TestRandomSamplingFacetsCollector extends FacetTestCase {
       doc.add(new FacetField("iMod10", Integer.toString(i % numCategories)));
       writer.addDocument(config.build(taxoWriter, doc));
     }
+    writer.forceMerge(CHI_SQUARE_VALUES.length - 1);
     
     // NRT open
     IndexSearcher searcher = newSearcher(writer.getReader());