diff --git a/include/mruby.h b/include/mruby.h
index 93aab5672..77f862356 100644
--- a/include/mruby.h
+++ b/include/mruby.h
@@ -44,6 +44,9 @@
 #include <limits.h>
 
 #ifdef __cplusplus
+#ifndef UINTPTR_MAX
+#error Must be placed `#include <mruby.h>` before `#include <stdint.h>`
+#endif
 #ifndef SIZE_MAX
 #ifdef __SIZE_MAX__
 #define SIZE_MAX __SIZE_MAX__