diff --git a/doc/emacs/help.texi b/doc/emacs/help.texi
index f15b4c5e89d..079ea76156f 100644
--- a/doc/emacs/help.texi
+++ b/doc/emacs/help.texi
@@ -322,6 +322,15 @@ file where it was defined, whether it has been declared obsolete, and
 yet further information is often reachable by clicking or typing
 @key{RET} on emphasized parts of the text.
 
+@cindex function type specifier
+
+The function type, if known, is expressed with a @dfn{function type
+specifier} (@pxref{Type Specifiers,,,elisp, The Emacs Lisp Reference
+Manual}), it will be specified if the type was manually declared by the
+programmer or inferred by the compiler.  Note that function type
+inference works only when native compilation is enabled (@pxref{native
+compilation,,, elisp, The Emacs Lisp Reference Manual}).
+
 @vindex help-enable-symbol-autoload
   If you request help for an autoloaded function whose @code{autoload}
 form (@pxref{Autoload,,, elisp, The Emacs Lisp Reference Manual})