diff --git a/etc/NEWS b/etc/NEWS
index 01b3ed3f2c1..5cb1af99b56 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -867,7 +867,8 @@ a typographically-correct documents.
 
 * Incompatible Lisp Changes in Emacs 25.1
 
-** Removed font-lock-beginning-of-syntax-function and the SYNTAX-BEGIN
+** `syntax-begin-function' is declared obsolete.
+Removed font-lock-beginning-of-syntax-function and the SYNTAX-BEGIN
 slot in font-lock-defaults.
 
 +++
diff --git a/lisp/emacs-lisp/syntax.el b/lisp/emacs-lisp/syntax.el
index fee62149b38..95ed775f6b4 100644
--- a/lisp/emacs-lisp/syntax.el
+++ b/lisp/emacs-lisp/syntax.el
@@ -374,6 +374,7 @@ from each other, to avoid keeping too much useless info.")
   "Function to move back outside of any comment/string/paren.
 This function should move the cursor back to some syntactically safe
 point (where the PPSS is equivalent to nil).")
+(make-obsolete-variable 'syntax-begin-function nil "25.1")
 
 (defvar syntax-ppss-cache nil
   "List of (POS . PPSS) pairs, in decreasing POS order.")