diff --git a/src/utils.scm b/src/utils.scm
index b70e359..1758a77 100644
--- a/src/utils.scm
+++ b/src/utils.scm
@@ -295,8 +295,11 @@
 	      (window-path dpy p)))))
 
 (define (window-viewable? dpy window)
-  (eq? (window-attribute:map-state (get-window-attributes dpy window))
-       (map-state is-viewable)))
+  (and window
+       (let ((attrs (get-window-attributes dpy window)))
+         (and attrs
+              (eq? (window-attribute:map-state attrs)
+                   (map-state is-viewable))))))
 
 (define (window-mapped? dpy window)
   (and window