diff -ru dbus.orig/dbus.scm dbus/dbus.scm
--- dbus.orig/dbus.scm	2014-06-19 15:02:24.000000000 +0400
+++ dbus/dbus.scm	2014-06-19 15:10:17.998005481 +0400
@@ -272,7 +272,7 @@
 	(define (tassq tree . keys)
 		(let ([key-list (if (pair? (car keys)) (car keys) keys)])
 			(let loop ([rem-keys key-list][subtree tree])
-				(if (null? rem-keys)
+				(if (or (not subtree) (null? rem-keys))
 					subtree
 					(loop (cdr rem-keys)
 						(let ([pr (assq (car rem-keys) subtree)])