diff --git a/src/shared/bus-wait-for-units.c b/src/shared/bus-wait-for-units.c
index 78b2a60403..ed0442f2c6 100644
--- a/src/shared/bus-wait-for-units.c
+++ b/src/shared/bus-wait-for-units.c
@@ -91,7 +91,8 @@ static void bus_wait_for_units_clear(BusWaitForUnits *d) {
         while ((item = hashmap_first(d->items))) {
                 d->current = item;
 
-                item->unit_callback(d, item->bus_path, false, item->userdata);
+                if (item->unit_callback)
+                        item->unit_callback(d, item->bus_path, false, item->userdata);
                 wait_for_item_free(item);
         }