diff --git a/units/user/systemd-tmpfiles-clean.service b/units/user/systemd-tmpfiles-clean.service
index 3be0de5f7d..b989d41373 100644
--- a/units/user/systemd-tmpfiles-clean.service
+++ b/units/user/systemd-tmpfiles-clean.service
@@ -19,3 +19,4 @@ Type=oneshot
 ExecStart=systemd-tmpfiles --user --clean
 SuccessExitStatus=DATAERR
 IOSchedulingClass=idle
+Slice=background.slice