diff --git a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/ByteBufferPool.java b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/ByteBufferPool.java
index bb2c978e09..aa5f8731c5 100644
--- a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/ByteBufferPool.java
+++ b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/ByteBufferPool.java
@@ -31,7 +31,7 @@ public interface ByteBufferPool {
    * new buffer.
    *
    * @param direct     Whether the buffer should be direct.
-   * @param minLength  The minimum length the buffer will have.
+   * @param length     The minimum length the buffer will have.
    * @return           A new ByteBuffer.  This ByteBuffer must be direct.
    *                   Its capacity can be less than what was requested, but
    *                   must be at least 1 byte.
diff --git a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/ElasticByteBufferPool.java b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/ElasticByteBufferPool.java
index f1ea9ff6b5..c4b4491ec3 100644
--- a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/ElasticByteBufferPool.java
+++ b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/ElasticByteBufferPool.java
@@ -52,6 +52,16 @@ public int compareTo(Key other) {
           compare(insertionTime, other.insertionTime).
           result();
     }
+
+    @Override
+    public boolean equals(Object rhs) {
+      try {
+        Key o = (Key)rhs;
+        return (compareTo(o) == 0);
+      } catch (ClassCastException e) {
+        return false;
+      }
+    }
   }
 
   private final TreeMap<Key, ByteBuffer> buffers =
diff --git a/hadoop-hdfs-project/hadoop-hdfs/CHANGES-HDFS-4949.txt b/hadoop-hdfs-project/hadoop-hdfs/CHANGES-HDFS-4949.txt
index 51af0b7aa3..cc6737bc97 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/CHANGES-HDFS-4949.txt
+++ b/hadoop-hdfs-project/hadoop-hdfs/CHANGES-HDFS-4949.txt
@@ -64,3 +64,5 @@ HDFS-4949 (Unreleased)
 
     HDFS-5210. Fix some failing unit tests on HDFS-4949 branch.
     (Contributed by Andrew Wang)
+
+    HDFS-5266. ElasticByteBufferPool#Key does not implement equals. (cnauroth)