diff --git a/src/core/exec-invoke.c b/src/core/exec-invoke.c
index cdfa9f823b..4b63e2a204 100644
--- a/src/core/exec-invoke.c
+++ b/src/core/exec-invoke.c
@@ -4061,7 +4061,7 @@ int exec_invoke(
         int r, ngids = 0;
         _cleanup_free_ gid_t *supplementary_gids = NULL;
         const char *username = NULL, *groupname = NULL;
-        _cleanup_free_ char *home_buffer = NULL, *memory_pressure_path = NULL;
+        _cleanup_free_ char *home_buffer = NULL, *memory_pressure_path = NULL, *own_user = NULL;
         const char *home = NULL, *shell = NULL;
         char **final_argv = NULL;
         dev_t journal_stream_dev = 0;
@@ -4298,8 +4298,23 @@ int exec_invoke(
                         username = runtime->dynamic_creds->user->name;
 
         } else {
-                if (context->user) {
-                        r = get_fixed_user(context->user, &username, &uid, &gid, &home, &shell);
+                const char *u;
+
+                if (context->user)
+                        u = context->user;
+                else if (context->pam_name) {
+                        /* If PAM is enabled but no user name is explicitly selected, then use our own one. */
+                        own_user = getusername_malloc();
+                        if (!own_user) {
+                                *exit_status = EXIT_USER;
+                                return log_exec_error_errno(context, params, r, "Failed to determine my own user ID: %m");
+                        }
+                        u = own_user;
+                } else
+                        u = NULL;
+
+                if (u) {
+                        r = get_fixed_user(u, &username, &uid, &gid, &home, &shell);
                         if (r < 0) {
                                 *exit_status = EXIT_USER;
                                 return log_exec_error_errno(context, params, r, "Failed to determine user credentials: %m");
diff --git a/test/units/TEST-74-AUX-UTILS.run.sh b/test/units/TEST-74-AUX-UTILS.run.sh
index 5b46e11409..3ef9c88d79 100755
--- a/test/units/TEST-74-AUX-UTILS.run.sh
+++ b/test/units/TEST-74-AUX-UTILS.run.sh
@@ -238,10 +238,13 @@ if [[ -e /usr/lib/pam.d/systemd-run0 ]] || [[ -e /etc/pam.d/systemd-run0 ]]; the
     run0 ls /
     assert_eq "$(run0 echo foo)" "foo"
     # Check if we set some expected environment variables
-    for arg in "" "--user=root" "--user=testuser"; do
+    for arg in "" "--user=root" "--user=0" "--user=testuser"; do
         assert_eq "$(run0 ${arg:+"$arg"} bash -c 'echo $SUDO_USER')" "$USER"
         assert_eq "$(run0 ${arg:+"$arg"} bash -c 'echo $SUDO_UID')" "$(id -u "$USER")"
         assert_eq "$(run0 ${arg:+"$arg"} bash -c 'echo $SUDO_GID')" "$(id -u "$USER")"
+
+        # Validate that we actually went properly through PAM (XDG_SESSION_TYPE is set by pam_systemd)
+        assert_eq "$(run0 ${arg:+"$arg"} bash -c 'echo $XDG_SESSION_TYPE')" "unspecified"
     done
     # Let's chain a couple of run0 calls together, for fun
     readarray -t cmdline < <(printf "%.0srun0\n" {0..31})