diff -r 59bf7f93c856 -r ea89c79affde src/signs_gui.cpp
--- a/src/signs_gui.cpp	Thu Mar 27 15:46:58 2008 +0000
+++ b/src/signs_gui.cpp	Thu Mar 27 15:48:54 2008 +0000
@@ -163,6 +163,7 @@
 struct editsign_d : querystr_d {
 	SignID cur_sign;
 };
+assert_compile(WINDOW_CUSTOM_SIZE >= sizeof(editsign_d));
 
 enum QueryEditSignWidgets {
 	QUERY_EDIT_SIGN_WIDGET_TEXT = 3,