@@ -14,10 +14,12 @@
  * file.
  */
 
 #import "OFDictionary.h"
 
+OF_ASSUME_NONNULL_BEGIN
+
 /*! @file */
 
 #ifdef OF_HAVE_BLOCKS
 /*!
  * @brief A block for replacing objects in an OFMutableDictionary.
@@ -24,11 +26,11 @@
  *
  * @param key The key of the object to replace
  * @param object The object to replace
  * @return The object to replace the object with
  */
-typedef id (^of_dictionary_replace_block_t)(id key, id object);
+typedef __nonnull id (^of_dictionary_replace_block_t)(id key, id object);
 #endif
 
 /*!
  * @class OFMutableDictionary OFDictionary.h ObjFW/OFDictionary.h
  *
@@ -103,5 +105,7 @@
 @end
 #if !defined(OF_HAVE_GENERICS) && !defined(DOXYGEN)
 # undef KeyType
 # undef ObjectType
 #endif
+
+OF_ASSUME_NONNULL_END