diff --git a/src/runtime/runtime-i18n.cc b/src/runtime/runtime-i18n.cc
index 75e0952..aeef25e 100644
--- a/src/runtime/runtime-i18n.cc
+++ b/src/runtime/runtime-i18n.cc
@@ -41,6 +41,7 @@
 #include "unicode/uloc.h"
 #include "unicode/unistr.h"
 #include "unicode/unum.h"
+#include "unicode/ustring.h"
 #include "unicode/uversion.h"