@@ -218,10 +218,17 @@
 
 		str = [OFMutableString stringWithString: @"<!--"];
 		[str appendString: comment];
 		[str appendString: @"-->"];
 
+		/*
+		 * Class swizzle the string to be immutable. We declared the
+		 * return type to be OFString*, so it can't be modified anyway.
+		 * But not swizzling it would create a real copy each time
+		 * -[copy] is called.
+		 */
+		str->isa = [OFString class];
 		return str;
 	}
 
 	pool = [[OFAutoreleasePool alloc] init];
 	def_ns = (defaultNamespace != nil