diff --git a/CHANGES.txt b/CHANGES.txt
index 00b6d8ea33..9f4a05d908 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -281,6 +281,9 @@ Trunk (unreleased changes)
     HADOOP-6504. Invalid example in the documentation of
     org.apache.hadoop.util.Tool. (Benoit Sigoure via tomwhite)
 
+    HADOOP-6546. BloomMapFile can return false negatives. (Clark Jefcoat
+    via tomwhite)
+
 Release 0.21.0 - Unreleased
 
   INCOMPATIBLE CHANGES
diff --git a/src/java/org/apache/hadoop/io/BloomMapFile.java b/src/java/org/apache/hadoop/io/BloomMapFile.java
index aa616a4565..17c5e5463c 100644
--- a/src/java/org/apache/hadoop/io/BloomMapFile.java
+++ b/src/java/org/apache/hadoop/io/BloomMapFile.java
@@ -58,6 +58,16 @@ public static void delete(FileSystem fs, String name) throws IOException {
     fs.delete(bloom, true);
     fs.delete(dir, true);
   }
+
+  private static byte[] byteArrayForBloomKey(DataOutputBuffer buf) {
+    int cleanLength = buf.getLength();
+    byte [] ba = buf.getData();
+    if (cleanLength != ba.length) {
+      ba = new byte[cleanLength];
+      System.arraycopy(buf.getData(), 0, ba, 0, cleanLength);
+    }
+    return ba;
+  }
   
   public static class Writer extends MapFile.Writer {
     private DynamicBloomFilter bloomFilter;
@@ -163,7 +173,7 @@ public synchronized void append(WritableComparable key, Writable val)
       super.append(key, val);
       buf.reset();
       key.write(buf);
-      bloomKey.set(buf.getData(), 1.0);
+      bloomKey.set(byteArrayForBloomKey(buf), 1.0);
       bloomFilter.add(bloomKey);
     }
 
@@ -228,7 +238,7 @@ public boolean probablyHasKey(WritableComparable key) throws IOException {
       }
       buf.reset();
       key.write(buf);
-      bloomKey.set(buf.getData(), 1.0);
+      bloomKey.set(byteArrayForBloomKey(buf), 1.0);
       return bloomFilter.membershipTest(bloomKey);
     }
     
diff --git a/src/test/core/org/apache/hadoop/io/TestBloomMapFile.java b/src/test/core/org/apache/hadoop/io/TestBloomMapFile.java
index 2a7d22455f..9cf0bbc2fa 100644
--- a/src/test/core/org/apache/hadoop/io/TestBloomMapFile.java
+++ b/src/test/core/org/apache/hadoop/io/TestBloomMapFile.java
@@ -18,6 +18,10 @@
 
 package org.apache.hadoop.io;
 
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.fs.FileSystem;
 import org.apache.hadoop.fs.Path;
@@ -67,4 +71,41 @@ public void testMembershipTest() throws Exception {
     assertTrue(falsePos < 2);
   }
 
+  private void checkMembershipVaryingSizedKeys(String name, List<Text> keys) throws Exception {
+    Path dirName = new Path(System.getProperty("test.build.data",".") +
+        name + ".bloommapfile"); 
+    FileSystem fs = FileSystem.getLocal(conf);
+    Path qualifiedDirName = fs.makeQualified(dirName);
+    BloomMapFile.Writer writer = new BloomMapFile.Writer(conf, fs,
+      qualifiedDirName.toString(), Text.class, NullWritable.class);
+    for (Text key : keys) {
+      writer.append(key, NullWritable.get());
+    }
+    writer.close();
+
+    // will check for membership in the opposite order of how keys were inserted
+    BloomMapFile.Reader reader = new BloomMapFile.Reader(fs,
+        qualifiedDirName.toString(), conf);
+    Collections.reverse(keys);
+    for (Text key : keys) {
+      assertTrue("False negative for existing key " + key, reader.probablyHasKey(key));
+    }
+    reader.close();
+    fs.delete(qualifiedDirName, true);
+  }
+
+  public void testMembershipVaryingSizedKeysTest1() throws Exception {
+    ArrayList<Text> list = new ArrayList<Text>();
+    list.add(new Text("A"));
+    list.add(new Text("BB"));
+    checkMembershipVaryingSizedKeys(getName(), list);
+  }
+
+  public void testMembershipVaryingSizedKeysTest2() throws Exception {
+    ArrayList<Text> list = new ArrayList<Text>();
+    list.add(new Text("AA"));
+    list.add(new Text("B"));
+    checkMembershipVaryingSizedKeys(getName(), list);
+  }
+
 }