diff --git a/src/java/com/samskivert/depot/CacheKey.java b/src/java/com/samskivert/depot/CacheKey.java
index 4c5d735..d84a234 100644
--- a/src/java/com/samskivert/depot/CacheKey.java
+++ b/src/java/com/samskivert/depot/CacheKey.java
@@ -35,8 +35,10 @@ public interface CacheKey
     public String getCacheId ();
 
     /**
-     * Returns the actual opaque serializable cache key under which results are stored
-     * in the cache identified by {@link #getCacheId}.
+     * Returns the actual opaque serializable cache key under which results are stored in the cache
+     * identified by {@link #getCacheId}. The object returned by this method should <em>only</em>
+     * reference system classes (not application classes). Depot takes care to ensure this and you
+     * probably aren't implementing your own cache keys so this should be fine.
      */
     public Serializable getCacheKey ();
 }
diff --git a/src/java/com/samskivert/depot/Key.java b/src/java/com/samskivert/depot/Key.java
index 46ff283..b91ff71 100644
--- a/src/java/com/samskivert/depot/Key.java
+++ b/src/java/com/samskivert/depot/Key.java
@@ -214,7 +214,7 @@ public class Key<T extends PersistentRecord> extends WhereClause
     // from CacheInvalidator
     public void invalidate (PersistenceContext ctx)
     {
-        ctx.cacheInvalidate(new KeyCacheKey(this));
+        ctx.cacheInvalidate(this);
     }
 
     /**
diff --git a/src/java/com/samskivert/depot/KeySet.java b/src/java/com/samskivert/depot/KeySet.java
index fd17a34..9754cca 100644
--- a/src/java/com/samskivert/depot/KeySet.java
+++ b/src/java/com/samskivert/depot/KeySet.java
@@ -300,7 +300,7 @@ public abstract class KeySet<T extends PersistentRecord> extends WhereClause
     // from ValidatingCacheInvalidator
     public void invalidate (PersistenceContext ctx) {
         for (Key<T> key : this) {
-            ctx.cacheInvalidate(new KeyCacheKey(key));
+            ctx.cacheInvalidate(key);
         }
     }
 
diff --git a/src/java/com/samskivert/depot/PersistenceContext.java b/src/java/com/samskivert/depot/PersistenceContext.java
index 65d905d..d9d080a 100644
--- a/src/java/com/samskivert/depot/PersistenceContext.java
+++ b/src/java/com/samskivert/depot/PersistenceContext.java
@@ -45,6 +45,7 @@ import com.samskivert.depot.annotation.TableGenerator;
 import com.samskivert.depot.impl.DepotMarshaller;
 import com.samskivert.depot.impl.DepotMetaData;
 import com.samskivert.depot.impl.DepotTypes;
+import com.samskivert.depot.impl.KeyCacheKey;
 import com.samskivert.depot.impl.Modifier;
 import com.samskivert.depot.impl.Operation;
 import com.samskivert.depot.impl.Query;
@@ -349,6 +350,19 @@ public class PersistenceContext
         }
     }
 
+    /**
+     * Evicts the cache entry indexed under the given key, if there is one.  The eviction may
+     * trigger further cache invalidations.
+     */
+    public void cacheInvalidate (Key<?> key)
+    {
+        if (key == null) {
+            log.warning("Cache key to invalidate must not be null.", new Exception());
+        } else {
+            cacheInvalidate(new KeyCacheKey(key));
+        }
+    }
+
     /**
      * Evicts the cache entry indexed under the given key, if there is one.  The eviction may
      * trigger further cache invalidations.