Index: src/OFObject.h
==================================================================
--- src/OFObject.h
+++ src/OFObject.h
@@ -23,10 +23,11 @@
 # define __STDC_CONSTANT_MACROS
 #endif
 
 #include <stddef.h>
 #include <stdint.h>
+#include <stdbool.h>
 #include <limits.h>
 
 #ifdef OF_OBJFW_RUNTIME
 # import "runtime.h"
 #else
@@ -74,10 +75,16 @@
 #if __has_feature(objc_bool)
 # undef YES
 # define YES __objc_yes
 # undef NO
 # define NO __objc_no
+# ifndef __cplusplus
+#  undef true
+#  define true ((bool)1)
+#  undef false
+#  define false ((bool)0)
+# endif
 #endif
 
 #if defined(__clang__) || __GCC_VERSION__ >= 406
 # define OF_SENTINEL __attribute__((sentinel))
 #else