@@ -160,10 +160,16 @@
 		@throw [OFInvalidEncodingException newWithClass: isa];
 
 	[ret appendCStringWithoutUTF8Checking: string + last
 				       length: i - last];
 
+	/*
+	 * 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.
+	 */
+	ret->isa = [OFString class];
 	return ret;
 }
 
 #ifdef OF_HAVE_BLOCKS
 - (OFString*)stringByXMLUnescapingWithBlock:
@@ -244,9 +250,15 @@
 		@throw [OFInvalidEncodingException newWithClass: isa];
 
 	[ret appendCStringWithoutUTF8Checking: string + last
 				       length: i - last];
 
+	/*
+	 * 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.
+	 */
+	ret->isa = [OFString class];
 	return ret;
 }
 #endif
 @end