diff --git a/validat0.cpp b/validat0.cpp
index b3bb80e5..b9ff1aaf 100644
--- a/validat0.cpp
+++ b/validat0.cpp
@@ -22,6 +22,7 @@
 
 #include <iostream>
 #include <iomanip>
+#include <sstream>
 
 #include "validate.h"