--- src/lread.c.orig	2014-11-04 20:29:22.129549000 +0100
+++ src/lread.c	2014-11-04 22:33:07.346414100 +0100
@@ -4351,6 +4351,12 @@
             } /* Vinstallation_directory != Vsource_directory */
 
         } /* if Vinstallation_directory */
+      else
+        {
+          Vsource_directory
+            = Fexpand_file_name (build_string ("../"),
+                                 Fcar (decode_env_path (0, PATH_DATA, 0)));
+        }
     }
   else                          /* !initialized */
     {