diff --git a/src/build_vehicle_gui.cpp b/src/build_vehicle_gui.cpp
--- a/src/build_vehicle_gui.cpp
+++ b/src/build_vehicle_gui.cpp
@@ -29,6 +29,7 @@
 #include "vehicle_func.h"
 #include "settings_type.h"
 #include "gfx_func.h"
+#include "widgets/dropdown_func.h"
 
 #include "table/sprites.h"
 #include "table/strings.h"