diff --git a/doc/emacs/package.texi b/doc/emacs/package.texi
index e6d0a66d571..2e3191440cb 100644
--- a/doc/emacs/package.texi
+++ b/doc/emacs/package.texi
@@ -611,6 +611,9 @@ regular package listing.  If you just wish to clone the source of a
 package, without adding it to the package list, use
 @code{package-vc-checkout}.
 
+  Note that currently, built-in packages cannot be upgraded using
+@code{package-vc-install}.
+
 @findex package-report-bug
 @findex package-vc-prepare-patch
   With the source checkout, you might want to reproduce a bug against
diff --git a/doc/misc/use-package.texi b/doc/misc/use-package.texi
index 6f51780057f..bcb068e6654 100644
--- a/doc/misc/use-package.texi
+++ b/doc/misc/use-package.texi
@@ -1660,7 +1660,8 @@ declaration.  The accepted property list is augmented by a @code{:rev}
 keyword, which has the same shape as the @code{REV} argument to
 @code{package-vc-install}.  Notably -- even when not specified --
 @code{:rev} defaults to checking out the last release of the package.
-You can use @code{:rev :newest} to check out the latest commit.
+You can use @code{:rev :newest} to check out the latest commit.  Note
+that currently, you cannot upgrade built-in packages using @code{:vc}.
 
 For example,