diff --git a/CHANGELOG.md b/CHANGELOG.md
index 31d12bdb..6354522e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,10 @@
 
 ## master (unreleased)
 
+### Changes
+
+* [cider#2903](https://github.com/clojure-emacs/cider/issues/2903): Avoid `No comment syntax is defined` prompts.
+
 ## 5.17.1 (2023-09-12)
 
 ### Changes
diff --git a/clojure-mode.el b/clojure-mode.el
index c242b2d7..5217c8b3 100644
--- a/clojure-mode.el
+++ b/clojure-mode.el
@@ -2084,7 +2084,7 @@ content) are considered part of the preceding sexp."
 (defun clojure-sort-ns ()
   "Internally sort each sexp inside the ns form."
   (interactive)
-  (comment-normalize-vars)
+  (comment-normalize-vars t) ;; `t`: avoid prompts
   (if (clojure-find-ns)
       (save-excursion
         (goto-char (match-beginning 0))
@@ -2230,7 +2230,7 @@ Returns a list pair, e.g. (\"defn\" \"abc\") or (\"deftest\" \"some-test\")."
 (defun clojure--looking-at-non-logical-sexp ()
   "Return non-nil if text after point is \"non-logical\" sexp.
 \"Non-logical\" sexp are ^metadata and #reader.macros."
-  (comment-normalize-vars)
+  (comment-normalize-vars t) ;; `t`: avoid prompts
   (comment-forward (point-max))
   (looking-at-p "\\(?:#?\\^\\)\\|#:?:?[[:alpha:]]"))