diff --git a/source/functions.h b/source/functions.h
index 8492899..63410aa 100644
--- a/source/functions.h
+++ b/source/functions.h
@@ -11,6 +11,7 @@
 #endif
 
 #include <fstream>
+#include <sstream>
 // #include <cpr/cpr.h>
 #include <curl/curl.h>