@@ -15,10 +15,12 @@
  * file.
  */
 
 #include "config.h"
 
+#define OF_XML_ELEMENT_M
+
 #include <stdlib.h>
 #include <string.h>
 
 #include <assert.h>
 
@@ -189,11 +191,12 @@
 - (instancetype)initWithElement: (OFXMLElement *)element
 {
 	self = [super of_init];
 
 	@try {
-		if (element == nil)
+		if (element == nil ||
+		    ![element isKindOfClass: [OFXMLElement class]])
 			@throw [OFInvalidArgumentException exception];
 
 		_name = [element->_name copy];
 		_namespace = [element->_namespace copy];
 		_defaultNamespace = [element->_defaultNamespace copy];
@@ -758,10 +761,13 @@
 	return [element autorelease];
 }
 
 - (void)addAttribute: (OFXMLAttribute *)attribute
 {
+	if (![attribute isKindOfClass: [OFXMLAttribute class]])
+		@throw [OFInvalidArgumentException exception];
+
 	if (_attributes == nil)
 		_attributes = [[OFMutableArray alloc] init];
 
 	if ([self attributeForName: attribute->_name
 			 namespace: attribute->_namespace] == nil)