diff --git a/optional/src/java/org/apache/commons/logging/impl/WeakHashtable.java b/optional/src/java/org/apache/commons/logging/impl/WeakHashtable.java
index 99c4309..a1ac64b 100644
--- a/optional/src/java/org/apache/commons/logging/impl/WeakHashtable.java
+++ b/optional/src/java/org/apache/commons/logging/impl/WeakHashtable.java
@@ -23,6 +23,8 @@ import java.util.*;
 /**
  * <p>Implementation of <code>Hashtable</code> that uses <code>WeakReference</code>'s
  * to hold it's keys thus allowing them to be reclaimed by the garbage collector.
+ * This class follows the symantics of <code>Hashtable</code> as closely as possible.
+ * It therefore does not accept null values or keys.
  * </p>
  * <p>
  * <strong>Usage:</strong> typical use case is as a drop-in replacement 
@@ -152,6 +154,14 @@ public final class WeakHashtable extends Hashtable {
      *@see Hashtable
      */    
     public Object put(Object key, Object value) {
+        // check for nulls, ensuring symantics match superclass
+        if (key == null) {
+            throw new NullPointerException("Null keys are not allowed");
+        }
+        if (value == null) {
+            throw new NullPointerException("Null values are not allowed");
+        }
+        
         Object result = null;
         Referenced lastValue = (Referenced) super.put(new Referenced(key), new Referenced(value));
         if (lastValue != null) {
diff --git a/optional/src/test/org/apache/commons/logging/impl/WeakHashtableTest.java b/optional/src/test/org/apache/commons/logging/impl/WeakHashtableTest.java
index 23ee252..f5c8e98 100644
--- a/optional/src/test/org/apache/commons/logging/impl/WeakHashtableTest.java
+++ b/optional/src/test/org/apache/commons/logging/impl/WeakHashtableTest.java
@@ -153,6 +153,24 @@ public class WeakHashtableTest extends TestCase {
         weakHashtable.put(anotherKey, new Long(1066));
         
         assertEquals(new Long(1066), weakHashtable.get(anotherKey));
+               
+        // Test compliance with the hashtable API re nulls
+        Exception caught = null;
+        try {
+            weakHashtable.put(null, new Object());
+        }
+        catch (Exception e) {
+            caught = e;
+        }
+        assertNotNull("did not throw an exception adding a null key", caught);
+        caught = null;
+        try {
+            weakHashtable.put(new Object(), null);
+        }
+        catch (Exception e) {
+            caught = e;
+        }
+        assertNotNull("did not throw an exception adding a null value", caught);
     }
     
     /** Tests public void putAll(MapÊt) */