diff --git a/lucene/facet/src/java/org/apache/lucene/facet/FacetsCollector.java b/lucene/facet/src/java/org/apache/lucene/facet/FacetsCollector.java
index 4f52d57..b7c1f1c 100644
--- a/lucene/facet/src/java/org/apache/lucene/facet/FacetsCollector.java
+++ b/lucene/facet/src/java/org/apache/lucene/facet/FacetsCollector.java
@@ -140,13 +140,21 @@ public final class FacetsCollector extends Collector {
   public final void setScorer(Scorer scorer) throws IOException {
     this.scorer = scorer;
   }
+  
+  /**
+   * creates a new FixedBitSet.
+   * This can be overridden for caching.
+   */
+  protected FixedBitSet newHitSet(int maxDoc) {
+    return new FixedBitSet(maxDoc);
+  }
     
   @Override
   public final void setNextReader(AtomicReaderContext context) throws IOException {
     if (bits != null) {
       matchingDocs.add(new MatchingDocs(this.context, bits, totalHits, scores));
     }
-    bits = new FixedBitSet(context.reader().maxDoc());
+    bits = newHitSet(context.reader().maxDoc());
     totalHits = 0;
     if (keepScores) {
       scores = new float[64]; // some initial size