diff --git a/src/support/unicode.cpp b/src/support/unicode.cpp
index 574d9f904f..8b0f9cb0db 100644
--- a/src/support/unicode.cpp
+++ b/src/support/unicode.cpp
@@ -23,6 +23,7 @@
 #include <cerrno>
 #include <map>
 #include <ostream>
+#include <string>
 
 
 using namespace std;