diff --git a/src/Magewire/Locker.php b/src/Magewire/Locker.php
index 8b4c5e3..458fb8d 100644
--- a/src/Magewire/Locker.php
+++ b/src/Magewire/Locker.php
@@ -73,8 +73,11 @@ public function evaluateCompletion(EvaluationResultFactory $resultFactory): Eval
         }
 
         if ($this->locker === null) {
-            return $resultFactory->createErrorMessageEvent(__('Please select locker'))
-                ->withCustomEvent('shipping:method:error');
+            $errorMessageEvent = $resultFactory->createErrorMessageEvent(__('Please select locker'))
+                ->withCustomEvent('shipping:method:error')
+                ->asError();
+            return $resultFactory->createValidation('validateInpostLocker')
+                ->withFailureResult($errorMessageEvent);
         }
 
         $quote = $this->session->getQuote();
diff --git a/src/view/frontend/layout/hyva_checkout_index_index.xml b/src/view/frontend/layout/hyva_checkout_index_index.xml
new file mode 100644
index 0000000..ef72ff5
--- /dev/null
+++ b/src/view/frontend/layout/hyva_checkout_index_index.xml
@@ -0,0 +1,10 @@
+<?xml version="1.0"?>
+<page xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+      xsi:noNamespaceSchemaLocation="urn:magento:framework:View/Layout/etc/page_configuration.xsd">
+    <body>
+        <referenceContainer name="hyva.checkout.init-evaluation.after">
+            <block name="hyva.checkout.init-evaluation.validate-inpost-locker"
+                   template="Snowdog_HyvaCheckoutInpost::validate-inpost-locker.phtml"/>
+        </referenceContainer>
+    </body>
+</page>
diff --git a/src/view/frontend/templates/validate-inpost-locker.phtml b/src/view/frontend/templates/validate-inpost-locker.phtml
new file mode 100644
index 0000000..d07f622
--- /dev/null
+++ b/src/view/frontend/templates/validate-inpost-locker.phtml
@@ -0,0 +1,8 @@
+<script>
+    hyvaCheckout.evaluation.registerValidator('validateInpostLocker', async (element, component) => {
+        return new Promise(resolve => {
+            let currentLocker = component.get('locker');
+            resolve(null !== currentLocker);
+        })
+    })
+</script>
