diff --git a/src/java/org/apache/lucene/store/RAMDirectory.java b/src/java/org/apache/lucene/store/RAMDirectory.java
index 8c2e0338478..d640ab5088d 100644
--- a/src/java/org/apache/lucene/store/RAMDirectory.java
+++ b/src/java/org/apache/lucene/store/RAMDirectory.java
@@ -173,7 +173,7 @@ public class RAMDirectory extends Directory implements Serializable {
   /** Removes an existing file in the directory.
    * @throws IOException if the file does not exist
    */
-  public synchronized final void deleteFile(String name) throws IOException {
+  public synchronized void deleteFile(String name) throws IOException {
     RAMFile file = (RAMFile)fileMap.get(name);
     if (file!=null) {
         fileMap.remove(name);
@@ -215,7 +215,7 @@ public class RAMDirectory extends Directory implements Serializable {
   }
 
   /** Returns a stream reading an existing file. */
-  public final IndexInput openInput(String name) throws IOException {
+  public IndexInput openInput(String name) throws IOException {
     RAMFile file;
     synchronized (this) {
       file = (RAMFile)fileMap.get(name);
diff --git a/src/test/org/apache/lucene/index/TestIndexReader.java b/src/test/org/apache/lucene/index/TestIndexReader.java
index 9b673345362..2516df05f2e 100644
--- a/src/test/org/apache/lucene/index/TestIndexReader.java
+++ b/src/test/org/apache/lucene/index/TestIndexReader.java
@@ -386,6 +386,38 @@ public class TestIndexReader extends TestCase
     }
 
 
+    // Make sure you can set norms & commit, and there are
+    // no extra norms files left:
+    public void testWritingNormsNoReader() throws IOException
+    {
+        Directory dir = new MockRAMDirectory();
+        IndexWriter writer = null;
+        IndexReader reader = null;
+        Term searchTerm = new Term("content", "aaa");
+
+        //  add 1 documents with term : aaa
+        writer  = new IndexWriter(dir, new WhitespaceAnalyzer(), true);
+        writer.setUseCompoundFile(false);
+        addDoc(writer, searchTerm.text());
+        writer.close();
+
+        //  now open reader & set norm for doc 0 (writes to
+        //  _0_1.s0)
+        reader = IndexReader.open(dir);
+        reader.setNorm(0, "content", (float) 2.0);
+        reader.close();
+        
+        //  now open reader again & set norm for doc 0 (writes to _0_2.s0)
+        reader = IndexReader.open(dir);
+        reader.setNorm(0, "content", (float) 2.0);
+        reader.close();
+        assertFalse("failed to remove first generation norms file on writing second generation",
+                    dir.fileExists("_0_1.s0"));
+        
+        dir.close();
+    }
+
+
     public void testDeleteReaderWriterConflictUnoptimized() throws IOException{
       deleteReaderWriterConflict(false);
     }
diff --git a/src/test/org/apache/lucene/store/MockRAMDirectory.java b/src/test/org/apache/lucene/store/MockRAMDirectory.java
index ca1e43f3260..101afd20105 100644
--- a/src/test/org/apache/lucene/store/MockRAMDirectory.java
+++ b/src/test/org/apache/lucene/store/MockRAMDirectory.java
@@ -19,8 +19,11 @@ package org.apache.lucene.store;
 
 import java.io.IOException;
 import java.io.File;
+import java.io.FileNotFoundException;
 import java.util.Iterator;
 import java.util.Random;
+import java.util.Map;
+import java.util.HashMap;
 
 /**
  * This is a subclass of RAMDirectory that adds methods
@@ -35,18 +38,37 @@ public class MockRAMDirectory extends RAMDirectory {
   long maxUsedSize;
   double randomIOExceptionRate;
   Random randomState;
+  boolean noDeleteOpenFile = true;
+
+  // NOTE: we cannot initialize the Map here due to the
+  // order in which our constructor actually does this
+  // member initialization vs when it calls super.  It seems
+  // like super is called, then our members are initialized:
+  Map openFiles;
 
   public MockRAMDirectory() throws IOException {
     super();
+    if (openFiles == null) {
+      openFiles = new HashMap();
+    }
   }
   public MockRAMDirectory(String dir) throws IOException {
     super(dir);
+    if (openFiles == null) {
+      openFiles = new HashMap();
+    }
   }
   public MockRAMDirectory(Directory dir) throws IOException {
     super(dir);
+    if (openFiles == null) {
+      openFiles = new HashMap();
+    }
   }
   public MockRAMDirectory(File dir) throws IOException {
     super(dir);
+    if (openFiles == null) {
+      openFiles = new HashMap();
+    }
   }
 
   public void setMaxSizeInBytes(long maxSize) {
@@ -67,6 +89,17 @@ public class MockRAMDirectory extends RAMDirectory {
     this.maxUsedSize = getRecomputedActualSizeInBytes();
   }
 
+  /**
+   * Emulate windows whereby deleting an open file is not
+   * allowed (raise IOException).
+  */
+  public void setNoDeleteOpenFile(boolean value) {
+    this.noDeleteOpenFile = value;
+  }
+  public boolean getNoDeleteOpenFile() {
+    return noDeleteOpenFile;
+  }
+
   /**
    * If 0.0, no exceptions will be thrown.  Else this should
    * be a double 0.0 - 1.0.  We will randomly throw an
@@ -91,7 +124,26 @@ public class MockRAMDirectory extends RAMDirectory {
     }
   }
 
+  public synchronized void deleteFile(String name) throws IOException {
+    synchronized(openFiles) {
+      if (noDeleteOpenFile && openFiles.containsKey(name)) {
+        throw new IOException("MockRAMDirectory: file \"" + name + "\" is still open: cannot delete");
+      }
+    }
+    super.deleteFile(name);
+  }
+
   public IndexOutput createOutput(String name) {
+    if (openFiles == null) {
+      openFiles = new HashMap();
+    }
+    synchronized(openFiles) {
+      if (noDeleteOpenFile && openFiles.containsKey(name)) {
+        // RuntimeException instead of IOException because
+        // super() does not throw IOException currently:
+        throw new RuntimeException("MockRAMDirectory: file \"" + name + "\" is still open: cannot overwrite");
+      }
+    }
     RAMFile file = new RAMFile(this);
     synchronized (this) {
       RAMFile existing = (RAMFile)fileMap.get(name);
@@ -105,6 +157,27 @@ public class MockRAMDirectory extends RAMDirectory {
     return new MockRAMOutputStream(this, file);
   }
 
+  public IndexInput openInput(String name) throws IOException {
+    RAMFile file;
+    synchronized (this) {
+      file = (RAMFile)fileMap.get(name);
+    }
+    if (file == null)
+      throw new FileNotFoundException(name);
+    else {
+      synchronized(openFiles) {
+        if (openFiles.containsKey(name)) {
+          Integer v = (Integer) openFiles.get(name);
+          v = new Integer(v.intValue()+1);
+          openFiles.put(name, v);
+        } else {
+          openFiles.put(name, new Integer(1));
+        }
+      }
+    }
+    return new MockRAMInputStream(this, name, file);
+  }
+
   /** Provided for testing purposes.  Use sizeInBytes() instead. */
   public synchronized final long getRecomputedSizeInBytes() {
     long size = 0;
diff --git a/src/test/org/apache/lucene/store/MockRAMInputStream.java b/src/test/org/apache/lucene/store/MockRAMInputStream.java
new file mode 100644
index 00000000000..4cf67053c34
--- /dev/null
+++ b/src/test/org/apache/lucene/store/MockRAMInputStream.java
@@ -0,0 +1,62 @@
+package org.apache.lucene.store;
+
+/**
+ * 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.
+ */
+
+/**
+ * Used by MockRAMDirectory to create an input stream that
+ * keeps track of when it's been closed.
+ */
+
+public class MockRAMInputStream extends RAMInputStream {
+  private MockRAMDirectory dir;
+  private String name;
+
+  /** Construct an empty output buffer. */
+  public MockRAMInputStream(MockRAMDirectory dir, String name, RAMFile f) {
+    super(f);
+    this.name = name;
+    this.dir = dir;
+  }
+
+  public void close() {
+    super.close();
+    synchronized(dir.openFiles) {
+      Integer v = (Integer) dir.openFiles.get(name);
+      if (v.intValue() == 1) {
+        dir.openFiles.remove(name);
+      } else {
+        v = new Integer(v.intValue()-1);
+        dir.openFiles.put(name, v);
+      }
+    }
+  }
+
+  public Object clone() {
+    MockRAMInputStream clone = (MockRAMInputStream) super.clone();
+    synchronized(dir.openFiles) {
+      if (dir.openFiles.containsKey(name)) {
+        Integer v = (Integer) dir.openFiles.get(name);
+        v = new Integer(v.intValue()+1);
+        dir.openFiles.put(name, v);
+      } else {
+        throw new RuntimeException("BUG: cloned file was not open?");
+      }
+    }
+    return clone;
+  }
+}