diff --git a/lisp/international/latexenc.el b/lisp/international/latexenc.el
index 6e2306449bc..66e3faa37b9 100644
--- a/lisp/international/latexenc.el
+++ b/lisp/international/latexenc.el
@@ -155,14 +155,16 @@ latexenc-find-file-coding-system
               (when (re-search-forward
                      "^%+ *\\(TeX-master\\|tex-main-file\\): *\"\\(.+\\)\""
                      nil t)
-                (let ((file (match-string 2)))
-                  (dolist (ext `("" ,(if (boundp 'TeX-default-extension)
-                                         (concat "." TeX-default-extension)
-                                       "")
-                                 ".tex" ".ltx" ".dtx" ".drv"))
-                    (if (and (null latexenc-main-file) ;Stop at first.
-                             (file-exists-p (concat file ext)))
-                        (setq latexenc-main-file (concat file ext)))))))
+                (let ((var (match-string 1))
+                      (file (match-string 2)))
+                  (when (safe-local-variable-p (intern var) file)
+                    (dolist (ext `("" ,(if (boundp 'TeX-default-extension)
+                                           (concat "." TeX-default-extension)
+                                         "")
+                                   ".tex" ".ltx" ".dtx" ".drv"))
+                      (if (and (null latexenc-main-file) ;Stop at first.
+                               (file-exists-p (concat file ext)))
+                          (setq latexenc-main-file (concat file ext))))))))
             ;; try tex-modes tex-guess-main-file
             (when (and (not latexenc-dont-use-tex-guess-main-file-flag)
                        (not latexenc-main-file))
diff --git a/lisp/textmodes/tex-mode.el b/lisp/textmodes/tex-mode.el
index 02ee1242c72..e7b1522751f 100644
--- a/lisp/textmodes/tex-mode.el
+++ b/lisp/textmodes/tex-mode.el
@@ -89,6 +89,7 @@ tex-main-file
 if the variable is non-nil."
   :type '(choice (const :tag "None" nil)
                  file)
+  :safe #'stringp
   :group 'tex-file)
 
 ;;;###autoload
@@ -2213,6 +2214,10 @@ tex-guess-main-file
 			  header-re (+ (point) 10000) t))))
 	    (throw 'found (expand-file-name buffer-file-name))))))))
 
+(unless (get 'TeX-master 'safe-local-variable) ;Don't override AUCTeX's setting.
+  (put 'TeX-master 'safe-local-variable
+       (lambda (x) (or (booleanp x) (stringp x)))))
+
 (defun tex-main-file ()
   "Return the relative name of the main file."
   (let* ((file (or tex-main-file