diff --git a/sudo.pod b/sudo.pod
index 40542b9b8..771ebc285 100644
--- a/sudo.pod
+++ b/sudo.pod
@@ -269,7 +269,9 @@ in L<passwd(@mansectform@)>.
 
 The B<-u> (I<user>) option causes B<sudo> to run the specified command
 as a user other than I<root>.  To specify a I<uid> instead of a
-I<username>, use I<#uid>.
+I<username>, use I<#uid>.  Note that if the I<targetpw> Defaults
+option is set (see L<sudoers(@mansectform@)>) it is not possible
+to run commands with a uid not listed in the password database.
 
 =item -v
 
diff --git a/sudoers.pod b/sudoers.pod
index 96a461ebd..0b128e438 100644
--- a/sudoers.pod
+++ b/sudoers.pod
@@ -408,7 +408,9 @@ password of the invoking user.  This flag is I<off> by default.
 
 If set, B<sudo> will prompt for the password of the user specified by
 the B<-u> flag (defaults to C<root>) instead of the password of the
-invoking user.  This flag is I<off> by default.
+invoking user.  Note that this precludes the use of a uid not listed
+in the passwd database as an argument to the B<-u> flag.
+This flag is I<off> by default.
 
 =item set_logname