Index: src/OFFileManager.m
==================================================================
--- src/OFFileManager.m
+++ src/OFFileManager.m
@@ -19,11 +19,11 @@
 
 #include <errno.h>
 #include <limits.h>
 #include "unistd_wrapper.h"
 
-#import "platform.h"
+#include "platform.h"
 
 #ifdef OF_PSP
 # include <sys/syslimits.h>
 #endif
 

Index: src/OFFileURIHandler.m
==================================================================
--- src/OFFileURIHandler.m
+++ src/OFFileURIHandler.m
@@ -23,11 +23,11 @@
 #ifdef HAVE_DIRENT_H
 # include <dirent.h>
 #endif
 #include "unistd_wrapper.h"
 
-#import "platform.h"
+#include "platform.h"
 #ifdef HAVE_SYS_STAT_H
 # include <sys/stat.h>
 #endif
 #include <sys/time.h>
 #ifdef OF_WINDOWS

Index: src/OFOnce.h
==================================================================
--- src/OFOnce.h
+++ src/OFOnce.h
@@ -13,11 +13,11 @@
  * file.
  */
 
 #include "objfw-defs.h"
 
-#include "platform.h"
+#import "macros.h"
 
 #if defined(OF_HAVE_PTHREADS)
 # include <pthread.h>
 typedef pthread_once_t OFOnceControl;
 # define OFOnceControlInitValue PTHREAD_ONCE_INIT
@@ -26,10 +26,12 @@
 # define OFOnceControlInitValue 0
 #elif defined(OF_AMIGAOS) || !defined(OF_HAVE_THREADS)
 typedef int OFOnceControl;
 # define OFOnceControlInitValue 0
 #endif
+
+OF_ASSUME_NONNULL_BEGIN
 
 #ifdef __cplusplus
 extern "C" {
 #endif
 /**
@@ -42,5 +44,7 @@
  */
 extern void OFOnce(OFOnceControl *control, void (*function)(void));
 #ifdef __cplusplus
 }
 #endif
+
+OF_ASSUME_NONNULL_END

Index: src/runtime/amiga-end.m
==================================================================
--- src/runtime/amiga-end.m
+++ src/runtime/amiga-end.m
@@ -13,11 +13,11 @@
  * file.
  */
 
 #include "config.h"
 
-#import "platform.h"
+#include "platform.h"
 
 #ifdef OF_MORPHOS
 __asm__ (
     ".section .eh_frame, \"aw\"\n"
     "	.long 0\n"

Index: src/runtime/private.h
==================================================================
--- src/runtime/private.h
+++ src/runtime/private.h
@@ -14,11 +14,10 @@
  */
 
 #include "config.h"
 
 #import "macros.h"
-#import "platform.h"
 
 #if !defined(__has_feature) || !__has_feature(nullability)
 # ifndef _Nonnull
 #  define _Nonnull
 # endif