Index: src/test/org/apache/commons/collections/keyvalue/TestMultiKey.java
===================================================================
--- src/test/org/apache/commons/collections/keyvalue/TestMultiKey.java	(revision 577164)
+++ src/test/org/apache/commons/collections/keyvalue/TestMultiKey.java	(working copy)
@@ -16,7 +16,15 @@
  */
 package org.apache.commons.collections.keyvalue;
 
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.ObjectInputStream;
+import java.io.ObjectOutputStream;
+import java.io.Serializable;
 import java.util.Arrays;
+import java.util.HashMap;
+import java.util.Map;
 
 import junit.framework.Assert;
 import junit.framework.Test;
@@ -206,4 +214,58 @@
         Assert.assertTrue(mk1.equals(null) == false);
     }
     
+    static class SystemHashCodeSimulatingKey implements Serializable {
+    	
+		private static final long serialVersionUID = 1L;
+		private final String name;
+    	private int hashCode = 1;
+
+		public SystemHashCodeSimulatingKey(String name)
+		{
+			this.name = name;
+		}
+
+		public boolean equals(Object obj)
+		{
+			return obj instanceof SystemHashCodeSimulatingKey 
+				&& name.equals(((SystemHashCodeSimulatingKey)obj).name);
+		}
+
+		public int hashCode()
+		{
+			return hashCode;
+		}
+
+		private Object readResolve() {
+			hashCode=2; // simulate different hashCode after deserialization in another process
+			return this;
+		}
+    }
+    
+    public void testEqualsAfterSerialization() throws IOException, ClassNotFoundException
+	{
+        SystemHashCodeSimulatingKey sysKey = new SystemHashCodeSimulatingKey("test");
+		MultiKey mk = new MultiKey(ONE, sysKey);
+        Map map = new HashMap();
+        map.put(mk, TWO);
+
+        // serialize
+        ByteArrayOutputStream baos = new ByteArrayOutputStream();
+        ObjectOutputStream out = new ObjectOutputStream(baos);
+        out.writeObject(sysKey);
+        out.writeObject(map);
+        out.close();
+
+        // deserialize
+        ByteArrayInputStream bais = new ByteArrayInputStream(baos.toByteArray());
+        ObjectInputStream in = new ObjectInputStream(bais);
+        sysKey = (SystemHashCodeSimulatingKey)in.readObject(); // simulate deserialization in another process
+        Map map2 = (Map) in.readObject();
+        in.close();
+
+        assertEquals(2, sysKey.hashCode()); // different hashCode now
+
+        MultiKey mk2 = new MultiKey(ONE, sysKey);
+        assertEquals(TWO, map2.get(mk2));		
+	}
 }
Index: src/java/org/apache/commons/collections/keyvalue/MultiKey.java
===================================================================
--- src/java/org/apache/commons/collections/keyvalue/MultiKey.java	(revision 577164)
+++ src/java/org/apache/commons/collections/keyvalue/MultiKey.java	(working copy)
@@ -16,6 +16,8 @@
  */
 package org.apache.commons.collections.keyvalue;
 
+import java.io.IOException;
+import java.io.ObjectInputStream;
 import java.io.Serializable;
 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(keys);
     }
     
     //-----------------------------------------------------------------------
@@ -255,4 +251,29 @@
         return "MultiKey" + Arrays.asList(keys).toString();
     }
 
+	/**
+	 * Calculate the hash code of the instance using the provided keys.
+	 * @param keys
+	 */
+	private void calculateHashCode(Object[] keys)
+	{
+		int total = 0;
+        for (int i = 0; i < keys.length; i++) {
+            if (keys[i] != null) {
+                total ^= keys[i].hashCode();
+            }
+        }
+        hashCode = total;
+	}
+	
+	/**
+	 * Recalculate the hash code after deserialization. The hash code of some
+	 * keys might have change (hash codes based on the system hash code are
+	 * only stable for the same process). 
+	 * @return the instance with recalculated hash code
+	 */
+	private Object readResolve() {
+		calculateHashCode(keys);
+		return this;
+	}
 }