Index: src/java/org/apache/commons/collections/keyvalue/MultiKey.java
===================================================================
--- src/java/org/apache/commons/collections/keyvalue/MultiKey.java	(revision 575016)
+++ src/java/org/apache/commons/collections/keyvalue/MultiKey.java	(working copy)
@@ -17,6 +17,8 @@
 package org.apache.commons.collections.keyvalue;
 
 import java.io.Serializable;
+import java.io.ObjectInputStream;
+import java.io.IOException;
 import java.util.Arrays;
 
 /** 
@@ -54,7 +56,7 @@
     /** The individual keys */
     private final Object[] keys;
     /** The cached hashCode */
-    private final int hashCode;
+    private transient int hashCode;
     
     /**
      * Constructor taking two keys.
@@ -164,13 +166,7 @@
             this.keys = keys;
         }
         
-        int total = 0;
-        for (int i = 0; i < keys.length; i++) {
-            if (keys[i] != null) {
-                total ^= keys[i].hashCode();
-            }
-        }
-        hashCode = total;
+        calculateHashCode();
     }
     
     //-----------------------------------------------------------------------
@@ -255,4 +251,29 @@
         return "MultiKey" + Arrays.asList(keys).toString();
     }
 
+    /**
+     * Calculate the cached hash code.
+     */
+    private void calculateHashCode() {
+       int total = 0;
+       for (int i = 0; i < keys.length; i++) {
+            if (keys[i] != null) {
+                total ^= keys[i].hashCode();
+            }
+        }
+       hashCode = total;
+    }
+
+    /**
+     * Recalculate the cached hashcode each time the multikey is deserialized.
+     *
+     * @param in 
+     * @throws IOException
+     * @throws ClassNotFoundException
+     */
+    private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException {
+        in.defaultReadObject();
+        calculateHashCode();
+    }
+
 }