diff --git a/root/root.cpp b/root/root.cpp
index d430b999..26e2e144 100644
--- a/root/root.cpp
+++ b/root/root.cpp
@@ -99,6 +99,7 @@
 #include <mutex>
 #include <list>
 #include <sstream>
+#include <iomanip>
 
 #include "geoip-html.h"