@@ -22,18 +22,18 @@
 /**
  * @class OFXMLAttribute OFXMLAttribute.h ObjFW/OFXMLAttribute.h
  *
  * @brief A representation of an attribute of an XML element as an object.
  */
+OF_SUBCLASSING_RESTRICTED
 @interface OFXMLAttribute: OFXMLNode
 {
 #if defined(OF_XML_ELEMENT_M) || defined(OF_XML_PARSER_M)
 @public
 #endif
 	OFString *_name, *_Nullable _namespace, *_stringValue;
 	bool _useDoubleQuotes;
-	OF_RESERVE_IVARS(OFXMLAttribute, 4)
 }
 
 /**
  * @brief The name of the attribute.
  */
@@ -89,11 +89,11 @@
  * @param stringValue The string value of the attribute
  * @return An initialized OFXMLAttribute with the specified parameters
  */
 - (instancetype)initWithName: (OFString *)name
 		   namespace: (nullable OFString *)nameSpace
-		 stringValue: (OFString *)stringValue;
+		 stringValue: (OFString *)stringValue OF_DESIGNATED_INITIALIZER;
 
 - (instancetype)initWithSerialization: (OFXMLElement *)element;
 @end
 
 OF_ASSUME_NONNULL_END