diff --git a/src/node_i18n.cc b/src/node_i18n.cc
index b337456c639318..fab594ce79b69e 100644
--- a/src/node_i18n.cc
+++ b/src/node_i18n.cc
@@ -43,6 +43,7 @@
 #include <unicode/ulocdata.h>
 #include <unicode/uvernum.h>
 #include <unicode/uversion.h>
+#include <unicode/ustring.h>
 
 #ifdef NODE_HAVE_SMALL_ICU
 /* if this is defined, we have a 'secondary' entry point.