diff --git a/bitlair_mqtt b/bitlair_mqtt
index 9ffd004..7caff0f 100644
--- a/bitlair_mqtt
+++ b/bitlair_mqtt
@@ -17,3 +17,10 @@ sub hook_checkout {
             for 1..$entry->quantity;
     }
 }
+
+sub hook_user_balance {
+    my ($class, $user, $old, $delta, $new, $transaction_id) = @_;
+
+    $mqtt->retain("bitlair/bank/cash" => -$new)
+        if $user eq "-cash";
+}