Index: lucene/core/src/java/org/apache/lucene/search/ConstantScoreAutoRewrite.java
===================================================================
--- lucene/core/src/java/org/apache/lucene/search/ConstantScoreAutoRewrite.java	(revision 1526306)
+++ lucene/core/src/java/org/apache/lucene/search/ConstantScoreAutoRewrite.java	(working copy)
@@ -96,17 +96,17 @@
     final int size = col.pendingTerms.size();
     if (col.hasCutOff) {
       return MultiTermQuery.CONSTANT_SCORE_FILTER_REWRITE.rewrite(reader, query);
-    } else if (size == 0) {
-      return getTopLevelQuery();
     } else {
       final BooleanQuery bq = getTopLevelQuery();
-      final BytesRefHash pendingTerms = col.pendingTerms;
-      final int sort[] = pendingTerms.sort(BytesRef.getUTF8SortedAsUnicodeComparator());
-      for(int i = 0; i < size; i++) {
-        final int pos = sort[i];
-        // docFreq is not used for constant score here, we pass 1
-        // to explicitely set a fake value, so it's not calculated
-        addClause(bq, new Term(query.field, pendingTerms.get(pos, new BytesRef())), 1, 1.0f, col.array.termState[pos]);
+      if (size > 0) {
+        final BytesRefHash pendingTerms = col.pendingTerms;
+        final int sort[] = pendingTerms.sort(BytesRef.getUTF8SortedAsUnicodeComparator());
+        for(int i = 0; i < size; i++) {
+          final int pos = sort[i];
+          // docFreq is not used for constant score here, we pass 1
+          // to explicitely set a fake value, so it's not calculated
+          addClause(bq, new Term(query.field, pendingTerms.get(pos, new BytesRef())), 1, 1.0f, col.array.termState[pos]);
+        }
       }
       // Strip scores
       final Query result = new ConstantScoreQuery(bq);
Index: lucene/core/src/java/org/apache/lucene/search/ScoringRewrite.java
===================================================================
--- lucene/core/src/java/org/apache/lucene/search/ScoringRewrite.java	(revision 1526306)
+++ lucene/core/src/java/org/apache/lucene/search/ScoringRewrite.java	(working copy)
@@ -87,9 +87,6 @@
     @Override
     public Query rewrite(IndexReader reader, MultiTermQuery query) throws IOException {
       final BooleanQuery bq = SCORING_BOOLEAN_QUERY_REWRITE.rewrite(reader, query);
-      // TODO: if empty boolean query return NullQuery?
-      if (bq.clauses().isEmpty())
-        return bq;
       // strip the scores off
       final Query result = new ConstantScoreQuery(bq);
       result.setBoost(query.getBoost());