diff --git a/src/citymania/cm_export.hpp b/src/citymania/cm_export.hpp
index b83259500a..aae016b6ce 100644
--- a/src/citymania/cm_export.hpp
+++ b/src/citymania/cm_export.hpp
@@ -1,6 +1,8 @@
 #ifndef CM_EXPORT_HPP
 #define CM_EXPORT_HPP
 
+#include <string>
+
 namespace citymania {
 
 void ExportOpenttdData(const std::string &filename);