diff --git a/style/amsmath.el b/style/amsmath.el
index 9d6944dc..c73f7475 100644
--- a/style/amsmath.el
+++ b/style/amsmath.el
@@ -163,24 +163,25 @@
    (TeX-run-style-hooks "amstext" "amsbsy" "amsopn")
 
    ;; RefTeX support: Tell RefTeX about amsmath environments.
-   (when (fboundp 'reftex-add-to-label-alist)
-     (reftex-add-to-label-alist '(AMSTeX)))
-
-   ;; Add \eqref to `reftex-ref-style-alist' and associate it to `e'
-   (when (and (boundp 'reftex-ref-style-alist)
-              ;; check if Emacs is already equipped with this
-              (not (assoc "AMSmath" reftex-ref-style-alist)))
-     ;; Append it to a local version in order to avoid a clash with
-     ;; user settings
-     (add-to-list (make-local-variable 'reftex-ref-style-alist)
-                  '("AMSmath" "amsmath" (("\\eqref" ?e)))
-                  t))
-
-   ;; Activate `AMSmath' when `LaTeX-reftex-ref-style-auto-activate'
-   ;; is non-nil
-   (and LaTeX-reftex-ref-style-auto-activate
-        (fboundp 'reftex-ref-style-activate)
-        (reftex-ref-style-activate "AMSmath"))
+   (when buffer-file-truename
+     (when (fboundp 'reftex-add-to-label-alist)
+       (reftex-add-to-label-alist '(AMSTeX)))
+
+     ;; Add \eqref to `reftex-ref-style-alist' and associate it to `e'
+     (when (and (boundp 'reftex-ref-style-alist)
+                ;; check if Emacs is already equipped with this
+                (not (assoc "AMSmath" reftex-ref-style-alist)))
+       ;; Append it to a local version in order to avoid a clash with
+       ;; user settings
+       (add-to-list (make-local-variable 'reftex-ref-style-alist)
+                    '("AMSmath" "amsmath" (("\\eqref" ?e)))
+                    t))
+
+     ;; Activate `AMSmath' when `LaTeX-reftex-ref-style-auto-activate'
+     ;; is non-nil
+     (and LaTeX-reftex-ref-style-auto-activate
+          (fboundp 'reftex-ref-style-activate)
+          (reftex-ref-style-activate "AMSmath")))
 
    (when (and (featurep 'font-latex)
               (eq TeX-install-font-lock 'font-latex-setup))