Index: lucene/facet/src/java/org/apache/lucene/facet/search/DrillSideways.java
===================================================================
--- lucene/facet/src/java/org/apache/lucene/facet/search/DrillSideways.java	(revision 1486738)
+++ lucene/facet/src/java/org/apache/lucene/facet/search/DrillSideways.java	(working copy)
@@ -410,8 +410,7 @@
                                                                       doMaxScore,
                                                                       true);
       DrillSidewaysResult r = search(query, hitCollector, fsp);
-      r.hits = hitCollector.topDocs();
-      return r;
+      return new DrillSidewaysResult(r.facetResults, hitCollector.topDocs());
     } else {
       return search(after, query, topN, fsp);
     }
@@ -425,8 +424,7 @@
                                     DrillDownQuery query, int topN, FacetSearchParams fsp) throws IOException {
     TopScoreDocCollector hitCollector = TopScoreDocCollector.create(Math.min(topN, searcher.getIndexReader().maxDoc()), after, true);
     DrillSidewaysResult r = search(query, hitCollector, fsp);
-    r.hits = hitCollector.topDocs();
-    return r;
+    return new DrillSidewaysResult(r.facetResults, hitCollector.topDocs());
   }
 
   /** Override this to use a custom drill-down {@link
@@ -454,16 +452,20 @@
     return false;
   }
 
-  /** Represents the returned result from a drill sideways
-   *  search. */
+  /**
+   * Represents the returned result from a drill sideways search. Note that if
+   * you called
+   * {@link DrillSideways#search(DrillDownQuery, Collector, FacetSearchParams)},
+   * then {@link #hits} will be {@code null}.
+   */
   public static class DrillSidewaysResult {
     /** Combined drill down & sideways results. */
     public final List<FacetResult> facetResults;
 
     /** Hits. */
-    public TopDocs hits;
+    public final TopDocs hits;
 
-    DrillSidewaysResult(List<FacetResult> facetResults, TopDocs hits) {
+    public DrillSidewaysResult(List<FacetResult> facetResults, TopDocs hits) {
       this.facetResults = facetResults;
       this.hits = hits;
     }