diff --git a/man/systemd.exec.xml b/man/systemd.exec.xml
index 699f6e263f..8079b4b210 100644
--- a/man/systemd.exec.xml
+++ b/man/systemd.exec.xml
@@ -1694,9 +1694,7 @@
         <term><varname>$SHELL</varname></term>
 
         <listitem><para>User name (twice), home directory, and the
-        login shell. The variables are set for the units that have
-        <varname>User=</varname> set, which includes user
-        <command>systemd</command> instances. See
+        login shell. See
         <citerefentry project='die-net'><refentrytitle>passwd</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
         </para></listitem>
       </varlistentry>
diff --git a/src/core/execute.c b/src/core/execute.c
index 47cc4311c1..67b54a3bec 100644
--- a/src/core/execute.c
+++ b/src/core/execute.c
@@ -815,13 +815,10 @@ static int get_fixed_user(const ExecContext *c, const char **user,
 
         assert(c);
 
-        if (!c->user)
-                return 0;
-
         /* Note that we don't set $HOME or $SHELL if they are not particularly enlightening anyway
          * (i.e. are "/" or "/bin/nologin"). */
 
-        name = c->user;
+        name = c->user ?: "root";
         r = get_user_creds_clean(&name, uid, gid, home, shell);
         if (r < 0)
                 return r;