diff -ur gzdoom-1.6.00.orig/src/gameconfigfile.cpp gzdoom-1.6.00/src/gameconfigfile.cpp
--- gzdoom-1.6.00.orig/src/gameconfigfile.cpp	2012-11-06 15:17:16.674596717 +0100
+++ gzdoom-1.6.00/src/gameconfigfile.cpp	2012-11-06 15:22:53.667933990 +0100
@@ -140,6 +140,7 @@
 #else
 		SetValueForKey ("Path", "~/" GAME_DIR, true);
 		SetValueForKey ("Path", SHARE_DIR, true);
+		SetValueForKey ("Path", "/usr/share/doom", true);
 #endif
 	}