diff --git a/src/gui.h b/src/gui.h
index f5f0570..a16f098 100644
--- a/src/gui.h
+++ b/src/gui.h
@@ -237,6 +237,16 @@
 # endif
 #endif
 
+#ifdef VIMDLL
+// Use spawn when GUI is starting.
+# define GUI_MAY_SPAWN
+
+// Uncomment the next definition if you want to use the `:gui` command on
+// Windows.  It uses `:mksession` to inherit the session from vim.exe to
+// gvim.exe.  So, it doesn't work perfectly. (EXPERIMENTAL)
+//# define EXPERIMENTAL_GUI_CMD
+#endif
+
 typedef struct Gui
 {
     int		in_focus;	    /* Vim has input focus */
@@ -245,6 +255,9 @@
     int		shell_created;	    /* Has the shell been created yet? */
     int		dying;		    /* Is vim dying? Then output to terminal */
     int		dofork;		    /* Use fork() when GUI is starting */
+#ifdef GUI_MAY_SPAWN
+    int		dospawn;	    /* Use spawn() when GUI is starting */
+#endif
     int		dragged_sb;	    /* Which scrollbar being dragged, if any? */
     win_T	*dragged_wp;	    /* Which WIN's sb being dragged, if any? */
     int		pointer_hidden;	    /* Is the mouse pointer hidden? */