diff --git a/lib/machine-loader.js b/lib/machine-loader.js
index 0fafb9ac..c60559c3 100644
--- a/lib/machine-loader.js
+++ b/lib/machine-loader.js
@@ -19,7 +19,7 @@ const unresponsiveStatus = { label: 'Unresponsive', type: 'error' }
 const stuckStatus = { label: 'Stuck', type: 'error' }
 
 const MACHINE_WITH_CALCULATED_FIELD_SQL = `
-select d.*, emptybills + regularbills as cashbox from devices d
+select d.*, COALESCE(emptybills, 0) + COALESCE(regularbills, 0) as cashbox from devices d
     left join (
       select count(*) as emptyBills, eub.device_id
         from empty_unit_bills eub