diff --git a/sessions_manager.hpp b/sessions_manager.hpp
index f9c00b5..ed3db49 100644
--- a/sessions_manager.hpp
+++ b/sessions_manager.hpp
@@ -7,6 +7,7 @@
 #include <map>
 #include <memory>
 #include <mutex>
+#include <string>
 
 namespace session
 {