Index: packfile.c
===================================================================
--- packfile.c	(revision 41199)
+++ packfile.c	(working copy)
@@ -4803,7 +4803,7 @@
     /* Add the include and dynext paths to the global search */
     parrot_split_path_ext(interp, path, &found_path, &found_ext);
     name_length = Parrot_str_length(interp, lang_name);
-    found_path = Parrot_str_substr(interp, found_path, -name_length, name_length, NULL, 0);
+    found_path = Parrot_str_substr(interp, found_path, 0, Parrot_str_length(interp, found_path)-name_length, NULL, 0);
     Parrot_lib_add_path(interp, Parrot_str_append(interp, found_path, CONST_STRING(interp, "include/")),
             PARROT_LIB_PATH_INCLUDE);
     Parrot_lib_add_path(interp, Parrot_str_append(interp, found_path, CONST_STRING(interp, "dynext/")),