diff --git a/CHANGES.txt b/CHANGES.txt
index 36d90a0969d..f942571c124 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -682,6 +682,9 @@ Release 0.21.1 - Unreleased
     HADOOP-7194. Fix resource leak in IOUtils.copyBytes(..).
     (Devaraj K via szetszwo)
 
+    HADOOP-7183. WritableComparator.get should not cache comparator objects.
+    (tomwhite via eli)
+
 Release 0.21.0 - 2010-08-13
 
   INCOMPATIBLE CHANGES
diff --git a/src/java/org/apache/hadoop/io/WritableComparator.java b/src/java/org/apache/hadoop/io/WritableComparator.java
index bfb16732222..cab52cf2bda 100644
--- a/src/java/org/apache/hadoop/io/WritableComparator.java
+++ b/src/java/org/apache/hadoop/io/WritableComparator.java
@@ -53,7 +53,6 @@ public class WritableComparator implements RawComparator {
       // if not, use the generic one
       if (comparator == null) {
         comparator = new WritableComparator(c, true);
-        comparators.put(c, comparator);
       }
     }
     return comparator;
@@ -75,7 +74,8 @@ public class WritableComparator implements RawComparator {
   } 
 
   /** Register an optimized comparator for a {@link WritableComparable}
-   * implementation. */
+   * implementation. Comparators registered with this method must be
+   * thread-safe. */
   public static synchronized void define(Class c,
                                          WritableComparator comparator) {
     comparators.put(c, comparator);