diff --git a/lisp/emacs-lisp/syntax.el b/lisp/emacs-lisp/syntax.el
index e1be301583..6b239c36c8 100644
--- a/lisp/emacs-lisp/syntax.el
+++ b/lisp/emacs-lisp/syntax.el
@@ -57,10 +57,12 @@ syntax-propertize-function
 It is the work horse of `syntax-propertize', which is called by things like
 Font-Lock and indentation.
 
-It is given two arguments, START and END: the start and end of the text to
-which `syntax-table' might need to be applied.  Major modes can use this to
-override the buffer's syntax table for special syntactic constructs that
-cannot be handled just by the buffer's syntax-table.
+It is given two arguments, START and END: the start and end of
+the text to which `syntax-table' might need to be applied.  It is
+called from within `with-silent-modifications'. Major modes can
+use this to override the buffer's syntax table for special
+syntactic constructs that cannot be handled just by the buffer's
+syntax-table.
 
 The specified function may call `syntax-ppss' on any position
 before END, but if it calls `syntax-ppss' on some
diff --git a/lisp/subr.el b/lisp/subr.el
index ca4d52535a..2b44a0316a 100644
--- a/lisp/subr.el
+++ b/lisp/subr.el
@@ -4608,7 +4608,8 @@ with-silent-modifications
 than cosmetic ones, undo data may become corrupted.
 
 This macro will run BODY normally, but doesn't count its buffer
-modifications as being buffer modifications.  This affects things
+modifications as being buffer modifications.  `inhibit-read-only'
+and 'inhibit-modification-hooks' are both t.  This affects things
 like `buffer-modified-p', checking whether the file is locked by
 someone else, running buffer modification hooks, and other things
 of that nature."