diff --git a/src/support/unicode.cpp b/src/support/unicode.cpp
index 35dde63014..cdcb7fd27e 100644
--- a/src/support/unicode.cpp
+++ b/src/support/unicode.cpp
@@ -22,6 +22,7 @@
 #include <cerrno>
 #include <iomanip>
 #include <map>
+#include <ostream>
 #include <string>
 
 using namespace std;