diff --git a/man/systemd.exec.xml b/man/systemd.exec.xml
index 7453aa7bee..dbe4594730 100644
--- a/man/systemd.exec.xml
+++ b/man/systemd.exec.xml
@@ -141,8 +141,13 @@
Group=
Set the UNIX user or group that the processes are executed as, respectively. Takes a single
- user or group name, or numeric ID as argument. If no group is set, the default group of the user is used. This
- setting does not affect commands whose command line is prefixed with +.
+ user or group name, or numeric ID as argument. For system services (services run by the system service manager,
+ i.e. managed by PID 1) and for user services of the root user (services managed by root's instance of
+ systemd --user), the default is root, but User= may be
+ used to specify a different user. For user services of any other user, switching user identity is not
+ permitted, hence the only valid setting is the same user the user's service manager is running as. If no group
+ is set, the default group of the user is used. This setting does not affect commands whose command line is
+ prefixed with +.