diff --git a/app/Http/ValidationRules/PaymentAmountsBalanceRule.php b/app/Http/ValidationRules/PaymentAmountsBalanceRule.php
index 13e6c57ecd1b..50d3cf4e601a 100644
--- a/app/Http/ValidationRules/PaymentAmountsBalanceRule.php
+++ b/app/Http/ValidationRules/PaymentAmountsBalanceRule.php
@@ -60,7 +60,7 @@ class PaymentAmountsBalanceRule implements Rule
         {
             foreach(request()->input('invoices') as $invoice)
             {
-                $invoice_amounts =+ $invoice['amount'];
+                $invoice_amounts += $invoice['amount'];
             }
         }
         else