diff --git a/src/java/com/samskivert/depot/Key.java b/src/java/com/samskivert/depot/Key.java
index 7da1ba4..5132ebb 100644
--- a/src/java/com/samskivert/depot/Key.java
+++ b/src/java/com/samskivert/depot/Key.java
@@ -44,7 +44,7 @@ import com.samskivert.depot.impl.ExpressionVisitor;
  * instantiated explicitly.
  */
 public class Key<T extends PersistentRecord> extends WhereClause
-    implements SQLExpression, ValidatingCacheInvalidator
+    implements ValidatingCacheInvalidator
 {
     /** Handles the matching of the key columns to its bound values. This is needed so that we can
      * combine a bunch of keys into a {@link KeySet}. */
diff --git a/src/java/com/samskivert/depot/impl/HSQLBuilder.java b/src/java/com/samskivert/depot/impl/HSQLBuilder.java
index 10f83a0..b5a7583 100644
--- a/src/java/com/samskivert/depot/impl/HSQLBuilder.java
+++ b/src/java/com/samskivert/depot/impl/HSQLBuilder.java
@@ -178,6 +178,8 @@ public class HSQLBuilder
                 return "week";
             case YEAR:
                 return "year";
+            case EPOCH:
+                throw new IllegalArgumentException("HSQL doesn't have a direct function for epoch");
             }
             throw new IllegalArgumentException("Unknown date part: " + part);
         }
diff --git a/src/java/com/samskivert/depot/operator/SQLOperator.java b/src/java/com/samskivert/depot/operator/SQLOperator.java
index 42e6439..ef84f79 100644
--- a/src/java/com/samskivert/depot/operator/SQLOperator.java
+++ b/src/java/com/samskivert/depot/operator/SQLOperator.java
@@ -56,7 +56,8 @@ public interface SQLOperator extends SQLExpression
             return builder.visit(this);
         }
 
-        // from SQLExpression
+
+        @Override // from SQLExpression
         public void addClasses (Collection<Class<? extends PersistentRecord>> classSet)
         {
             for (SQLExpression operand : _args) {