diff --git a/src/core/dbus-unit.c b/src/core/dbus-unit.c
index 53daa9c2ec..220b4c2372 100644
--- a/src/core/dbus-unit.c
+++ b/src/core/dbus-unit.c
@@ -1062,7 +1062,7 @@ static int append_cgroup(sd_bus_message *reply, const char *p, Set *pids) {
                 if (r == 0)
                         break;
 
-                j = path_join(p, g);
+                j = path_join(empty_to_root(p), g);
                 if (!j)
                         return -ENOMEM;