Index: lucene/core/src/java/org/apache/lucene/search/ConstantScoreAutoRewrite.java
===================================================================
--- lucene/core/src/java/org/apache/lucene/search/ConstantScoreAutoRewrite.java	(revision 1526301)
+++ lucene/core/src/java/org/apache/lucene/search/ConstantScoreAutoRewrite.java	(working copy)
@@ -97,7 +97,9 @@
     if (col.hasCutOff) {
       return MultiTermQuery.CONSTANT_SCORE_FILTER_REWRITE.rewrite(reader, query);
     } else if (size == 0) {
-      return getTopLevelQuery();
+      final Query result = new ConstantScoreQuery(getTopLevelQuery());
+      result.setBoost(query.getBoost());
+      return result;
     } else {
       final BooleanQuery bq = getTopLevelQuery();
       final BytesRefHash pendingTerms = col.pendingTerms;