@@ -471,11 +471,11 @@
 	}
 
 	return self;
 }
 
-- (id)objectForKey: (id)key
+- (id)objectForKey: (id <OFCopying>)key
 {
 	uint32_t i, hash, last;
 
 	if (key == nil)
 		@throw [OFInvalidArgumentException newWithClass: isa