diff --git a/include/mruby.h b/include/mruby.h
index f2c800eec..d891d0f5c 100644
--- a/include/mruby.h
+++ b/include/mruby.h
@@ -34,6 +34,7 @@
 #define __STDC_FORMAT_MACROS
 #endif
 
+#include <stdarg.h>
 #include <stdint.h>
 #include <stddef.h>
 #include <limits.h>