diff --git a/lisp/gnus/nnselect.el b/lisp/gnus/nnselect.el
index 66577282a0f..7d8d28ac431 100644
--- a/lisp/gnus/nnselect.el
+++ b/lisp/gnus/nnselect.el
@@ -440,7 +440,7 @@ artlist; otherwise store the ARTLIST in the group parameters."
       (if (eq 'nnselect (car (gnus-server-to-method server)))
 	  (with-current-buffer gnus-summary-buffer
 	    (let ((thread (gnus-id-to-thread article)))
-	      (when thread
+              (when (car thread)
 		(mapc
 		 (lambda (x)
 		   (when (and x (> x 0))