diff --git a/src/h2load_http2_session.cc b/src/h2load_http2_session.cc
index 3adda1ff..bc658380 100644
--- a/src/h2load_http2_session.cc
+++ b/src/h2load_http2_session.cc
@@ -25,6 +25,7 @@
 #include "h2load_http2_session.h"
 
 #include <cassert>
+#include <cerrno>
 
 #include "h2load.h"
 #include "util.h"