@@ -16,10 +16,12 @@
 
 #import "OFObject.h"
 #import "OFSerialization.h"
 #import "OFMessagePackRepresentation.h"
 
+OF_ASSUME_NONNULL_BEGIN
+
 @class OFString;
 @class OFURL;
 
 /*!
  * @class OFDataArray OFDataArray.h ObjFW/OFDataArray.h
@@ -228,18 +230,18 @@
 /*!
  * @brief Returns the first item of the OFDataArray.
  *
  * @return The first item of the OFDataArray or NULL
  */
-- (void*)firstItem OF_RETURNS_INNER_POINTER;
+- (nullable void*)firstItem OF_RETURNS_INNER_POINTER;
 
 /*!
  * @brief Returns the last item of the OFDataArray.
  *
  * @return The last item of the OFDataArray or NULL
  */
-- (void*)lastItem OF_RETURNS_INNER_POINTER;
+- (nullable void*)lastItem OF_RETURNS_INNER_POINTER;
 
 /*!
  * @brief Adds an item to the OFDataArray.
  *
  * @param item A pointer to an arbitrary item
@@ -323,8 +325,10 @@
  * @param path The path of the file to write to
  */
 - (void)writeToFile: (OFString*)path;
 #endif
 @end
+
+OF_ASSUME_NONNULL_END
 
 #import "OFDataArray+Hashing.h"
 #import "OFDataArray+MessagePackValue.h"