Index: src/objc_sync.m
==================================================================
--- src/objc_sync.m
+++ src/objc_sync.m
@@ -17,10 +17,12 @@
 #include "config.h"
 
 #include <stdio.h>
 #include <stdlib.h>
 #include <assert.h>
+
+#include <sys/types.h>
 
 #ifdef OF_OBJFW_RUNTIME
 # import <objfw-rt.h>
 #else
 # import <objc/objc.h>