diff --git a/src/SIE/Data/Verification.php b/src/SIE/Data/Verification.php
index 3aaf336..a7717c5 100644
--- a/src/SIE/Data/Verification.php
+++ b/src/SIE/Data/Verification.php
@@ -147,7 +147,7 @@ public function validate(): void
             // validate all our transactions
             $transaction->validate();
             // calculate sum of all transactions
-            $sum += $transaction->getAmount();
+            $sum += (float) $transaction->getAmount();
         }
 
         // validate that our transactions equal zero