@@ -14,10 +14,12 @@
  * file.
  */
 
 #import "OFSet.h"
 
+OF_ASSUME_NONNULL_BEGIN
+
 /*!
  * @class OFMutableSet OFSet.h ObjFW/OFSet.h
  *
  * @brief An abstract class for a mutable unordered set of unique objects.
  */
@@ -71,5 +73,7 @@
 - (void)makeImmutable;
 @end
 #if !defined(OF_HAVE_GENERICS) && !defined(DOXYGEN)
 # undef ObjectType
 #endif
+
+OF_ASSUME_NONNULL_END