diff --git a/lucene/core/src/test/org/apache/lucene/index/TestDuelingCodecs.java b/lucene/core/src/test/org/apache/lucene/index/TestDuelingCodecs.java
index 5535b11df0a..f8bfd0ed66b 100644
--- a/lucene/core/src/test/org/apache/lucene/index/TestDuelingCodecs.java
+++ b/lucene/core/src/test/org/apache/lucene/index/TestDuelingCodecs.java
@@ -37,17 +37,17 @@ import java.util.Random;
  * Compares one codec against another
  */
 public class TestDuelingCodecs extends LuceneTestCase {
-  private Directory leftDir;
-  private IndexReader leftReader;
-  private Codec leftCodec;
+  Directory leftDir;
+  IndexReader leftReader;
+  Codec leftCodec;
 
-  private Directory rightDir;
-  private IndexReader rightReader;
-  private Codec rightCodec;
-  private RandomIndexWriter leftWriter;
-  private RandomIndexWriter rightWriter;
-  private long seed;
-  private String info;  // for debugging
+  Directory rightDir;
+  IndexReader rightReader;
+  Codec rightCodec;
+  RandomIndexWriter leftWriter;
+  RandomIndexWriter rightWriter;
+  long seed;
+  String info;  // for debugging
 
   @Override
   public void setUp() throws Exception {
@@ -143,8 +143,9 @@ public class TestDuelingCodecs extends LuceneTestCase {
   /**
    * checks the two indexes are equivalent
    */
+  // we use a small amount of docs here, so it works with any codec 
   public void testEquals() throws IOException {
-    int numdocs = TEST_NIGHTLY ? atLeast(2000) : atLeast(100);
+    int numdocs = atLeast(100);
     createRandomIndex(numdocs, leftWriter, seed);
     createRandomIndex(numdocs, rightWriter, seed);
 
diff --git a/lucene/core/src/test/org/apache/lucene/index/TestDuelingCodecsAtNight.java b/lucene/core/src/test/org/apache/lucene/index/TestDuelingCodecsAtNight.java
new file mode 100644
index 00000000000..08479b4e526
--- /dev/null
+++ b/lucene/core/src/test/org/apache/lucene/index/TestDuelingCodecsAtNight.java
@@ -0,0 +1,41 @@
+package org.apache.lucene.index;
+
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import org.apache.lucene.util.LuceneTestCase.Nightly;
+import org.apache.lucene.util.LuceneTestCase.SuppressCodecs;
+
+/**
+ * Just like TestDuelingCodecs, only with a lot more documents.
+ */
+@Nightly
+@SuppressCodecs({"Memory", "Direct"}) // it can be too much for these codecs
+public class TestDuelingCodecsAtNight extends TestDuelingCodecs {
+
+  // use a big number of documents
+  public void testBigEquals() throws Exception {
+    int numdocs = atLeast(2000);
+    createRandomIndex(numdocs, leftWriter, seed);
+    createRandomIndex(numdocs, rightWriter, seed);
+
+    leftReader = leftWriter.getReader();
+    rightReader = rightWriter.getReader();
+    
+    assertReaderEquals(info, leftReader, rightReader);
+  }
+}