diff --git a/src/Action/Admin/RefundUnitsAction.php b/src/Action/Admin/RefundUnitsAction.php
index 0aee8e9d..be133fc2 100644
--- a/src/Action/Admin/RefundUnitsAction.php
+++ b/src/Action/Admin/RefundUnitsAction.php
@@ -4,7 +4,9 @@
 
 namespace Sylius\RefundPlugin\Action\Admin;
 
+use Psr\Log\LoggerInterface;
 use Sylius\RefundPlugin\Creator\RefundUnitsCommandCreatorInterface;
+use Sylius\RefundPlugin\Exception\InvalidRefundAmountException;
 use Symfony\Component\HttpFoundation\RedirectResponse;
 use Symfony\Component\HttpFoundation\Request;
 use Symfony\Component\HttpFoundation\Response;
@@ -27,16 +29,21 @@ final class RefundUnitsAction
     /** @var RefundUnitsCommandCreatorInterface */
     private $commandCreator;
 
+    /** @var LoggerInterface */
+    private $logger;
+
     public function __construct(
         MessageBusInterface $commandBus,
         Session $session,
         UrlGeneratorInterface $router,
-        RefundUnitsCommandCreatorInterface $commandCreator
+        RefundUnitsCommandCreatorInterface $commandCreator,
+        LoggerInterface $logger
     ) {
         $this->commandBus = $commandBus;
         $this->session = $session;
         $this->router = $router;
         $this->commandCreator = $commandCreator;
+        $this->logger = $logger;
     }
 
     public function __invoke(Request $request): Response
@@ -45,17 +52,32 @@ public function __invoke(Request $request): Response
             $this->commandBus->dispatch($this->commandCreator->fromRequest($request));
 
             $this->session->getFlashBag()->add('success', 'sylius_refund.units_successfully_refunded');
-        } catch (\InvalidArgumentException $exception) {
+        } catch (InvalidRefundAmountException $exception) {
             $this->session->getFlashBag()->add('error', $exception->getMessage());
+
+            $this->logger->error($exception->getMessage());
         } catch (HandlerFailedException $exception) {
             /** @var \Exception $previousException */
             $previousException = $exception->getPrevious();
 
-            $this->session->getFlashBag()->add('error', $previousException->getMessage());
+            $this->provideErrorMessage($previousException);
+
+            $this->logger->error($previousException->getMessage());
         }
 
         return new RedirectResponse($this->router->generate(
             'sylius_refund_order_refunds_list', ['orderNumber' => $request->attributes->get('orderNumber')]
         ));
     }
+
+    private function provideErrorMessage(\Exception $previousException): void
+    {
+        if ($previousException instanceof InvalidRefundAmountException) {
+            $this->session->getFlashBag()->add('error', $previousException->getMessage());
+
+            return;
+        }
+
+        $this->session->getFlashBag()->add('error', 'sylius_refund.error_occurred');
+    }
 }
diff --git a/src/Creator/RefundUnitsCommandCreator.php b/src/Creator/RefundUnitsCommandCreator.php
index 61779daf..0916a273 100644
--- a/src/Creator/RefundUnitsCommandCreator.php
+++ b/src/Creator/RefundUnitsCommandCreator.php
@@ -6,6 +6,7 @@
 
 use Sylius\RefundPlugin\Calculator\UnitRefundTotalCalculatorInterface;
 use Sylius\RefundPlugin\Command\RefundUnits;
+use Sylius\RefundPlugin\Exception\InvalidRefundAmountException;
 use Sylius\RefundPlugin\Model\OrderItemUnitRefund;
 use Sylius\RefundPlugin\Model\RefundType;
 use Sylius\RefundPlugin\Model\ShipmentRefund;
@@ -30,10 +31,9 @@ public function fromRequest(Request $request): RefundUnits
         $units = $this->filterEmptyRefundUnits($request->request->get('sylius_refund_units', []));
         $shipments = $this->filterEmptyRefundUnits($request->request->get('sylius_refund_shipments', []));
 
-        Assert::false(
-            count($units) === 0 && count($shipments) === 0,
-            'sylius_refund.at_least_one_unit_should_be_selected_to_refund'
-        );
+        if (count($units) === 0 && count($shipments) === 0) {
+            throw InvalidRefundAmountException::withValidationConstraint('sylius_refund.at_least_one_unit_should_be_selected_to_refund');
+        }
 
         return new RefundUnits(
             $request->attributes->get('orderNumber'),
diff --git a/src/Resources/config/services/actions.xml b/src/Resources/config/services/actions.xml
index 540db118..922b04e1 100644
--- a/src/Resources/config/services/actions.xml
+++ b/src/Resources/config/services/actions.xml
@@ -29,6 +29,7 @@
             <argument type="service" id="session" />
             <argument type="service" id="router" />
             <argument type="service" id="Sylius\RefundPlugin\Creator\RefundUnitsCommandCreator" />
+            <argument type="service" id="monolog.logger" />
         </service>
 
         <service id="Sylius\RefundPlugin\Action\CompleteRefundPaymentAction">
diff --git a/src/Resources/translations/flashes.en.yml b/src/Resources/translations/flashes.en.yml
index 868fe157..97bfa9fb 100644
--- a/src/Resources/translations/flashes.en.yml
+++ b/src/Resources/translations/flashes.en.yml
@@ -8,3 +8,4 @@ sylius_refund:
     resend_credit_memo_success: 'Selected credit memo has been successfully resent'
     unit_refund_exceeded: 'You cannot refund more money than the order unit total'
     units_successfully_refunded: 'Selected order units have been successfully refunded'
+    error_occurred: 'Unexpected error occurred'