Clarify warning about unknown articles in Gnus

* lisp/gnus/gnus-sum.el (gnus-summary-mark-article-as-unread)
(gnus-mark-article-as-unread): Clarify warning (bug#34990).

1 files changed, 2 insertions, 2 deletions

diff --git a/lisp/gnus/gnus-sum.el b/lisp/gnus/gnus-sum.el
index 7f6b936383c..019b47d67ef 100644
--- a/lisp/gnus/gnus-sum.el
+++ b/lisp/gnus/gnus-sum.el
@@ -11153,7 +11153,7 @@ If NO-EXPIRE, auto-expiry will be inhibited."
         t
       (if (<= article 0)
           (progn
-            (gnus-error 1 "Can't mark negative article numbers")
+            (gnus-error 1 "Gnus doesn't know the article number; can't mark")
             nil)
         (setq gnus-newsgroup-marked (delq article gnus-newsgroup-marked))
         (setq gnus-newsgroup-spam-marked
@@ -11326,7 +11326,7 @@ If NO-EXPIRE, auto-expiry will be inhibited."
   (let ((mark (or mark gnus-ticked-mark)))
     (if (<= article 0)
         (progn
-          (gnus-error 1 "Can't mark negative article numbers")
+          (gnus-error 1 "Gnus doesn't know the article number; can't mark")
           nil)
       (setq gnus-newsgroup-marked (delq article gnus-newsgroup-marked)
             gnus-newsgroup-spam-marked (delq article gnus-newsgroup-spam-marked)