diff --git a/src/shrpx_io_control.h b/src/shrpx_io_control.h
index 9baf95aa..d427fcbc 100644
--- a/src/shrpx_io_control.h
+++ b/src/shrpx_io_control.h
@@ -27,6 +27,7 @@
 
 #include "shrpx.h"
 
+#include <cinttypes>
 #include <vector>
 
 #include <ev.h>