diff -r 3988d0156a49 -r 416385a64dcb src/group_gui.cpp
--- a/src/group_gui.cpp	Fri Mar 28 16:33:28 2008 +0000
+++ b/src/group_gui.cpp	Fri Mar 28 16:34:50 2008 +0000
@@ -29,6 +29,20 @@
 #include "table/strings.h"
 #include "table/sprites.h"
 
+struct grouplist_d {
+	const Group **sort_list;
+	list_d l;                   // General list struct
+};
+assert_compile(WINDOW_CUSTOM_SIZE >= sizeof(grouplist_d));
+
+struct groupveh_d : vehiclelist_d {
+	GroupID group_sel;
+	VehicleID vehicle_sel;
+
+	grouplist_d gl;
+};
+assert_compile(WINDOW_CUSTOM_SIZE >= sizeof(groupveh_d));
+
 struct Sorting {
 	Listing aircraft;
 	Listing roadveh;