@@ -14,10 +14,12 @@
  * file.
  */
 
 #import "OFXMLNode.h"
 
+OF_ASSUME_NONNULL_BEGIN
+
 @class OFString;
 
 /*!
  * @class OFXMLAttribute OFXMLAttribute.h ObjFW/OFXMLAttribute.h
  *
@@ -30,13 +32,13 @@
 }
 
 #ifdef OF_HAVE_PROPERTIES
 @property (readonly, copy) OFString *name;
 # ifdef __cplusplus
-@property (readonly, copy, getter=namespace) OFString *namespace_;
+@property (readonly, copy, getter=namespace, nullable) OFString *namespace_;
 # else
-@property (readonly, copy) OFString *namespace;
+@property (readonly, copy, nullable) OFString *namespace;
 # endif
 #endif
 
 /*!
  * @brief Creates a new XML attribute.
@@ -55,11 +57,11 @@
  * @param namespace_ The namespace of the attribute
  * @param stringValue The string value of the attribute
  * @return A new autoreleased OFXMLAttribute with the specified parameters
  */
 + (instancetype)attributeWithName: (OFString*)name
-			namespace: (OFString*)namespace_
+			namespace: (nullable OFString*)namespace_
 		      stringValue: (OFString*)stringValue;
 
 /*!
  * @brief Initializes an already allocated OFXMLAttribute.
  *
@@ -77,11 +79,11 @@
  * @param namespace_ The namespace of the attribute
  * @param stringValue The string value of the attribute
  * @return An initialized OFXMLAttribute with the specified parameters
  */
 - initWithName: (OFString*)name
-     namespace: (OFString*)namespace_
+     namespace: (nullable OFString*)namespace_
    stringValue: (OFString*)stringValue;
 
 /*!
  * @brief Returns the name of the attribute as an autoreleased OFString.
  *
@@ -92,7 +94,9 @@
 /*!
  * @brief Returns the namespace of the attribute as an autoreleased OFString.
  *
  * @return The namespace of the attribute as an autoreleased OFString
  */
-- (OFString*)namespace;
+- (nullable OFString*)namespace;
 @end
+
+OF_ASSUME_NONNULL_END