diff --git a/.docker/config/simplesaml/metadata/saml20-idp-remote.php b/.docker/config/simplesaml/metadata/saml20-idp-remote.php
index 67d4ea76d..514b664f4 100644
--- a/.docker/config/simplesaml/metadata/saml20-idp-remote.php
+++ b/.docker/config/simplesaml/metadata/saml20-idp-remote.php
@@ -47,6 +47,7 @@
 $metadata[$idpEntityId] = [
   'entityid' => $idpEntityId,
   'contacts' => [],
+  'errorURL' => getenv('SIMPLESAMLPHP_SP_ERROR_URL') ?: null,
   'metadata-set' => 'saml20-idp-remote',
   'sign.authnrequest' => filter_var(getenv('SIMPLESAMLPHP_IDP_SIGN_AUTH'), FILTER_VALIDATE_BOOLEAN, FILTER_NULL_ON_FAILURE) ?? true,
   'SingleSignOnService' => [],
diff --git a/.docker/images/nginx/location_prepend_simplesamlphp.conf b/.docker/images/nginx/location_prepend_simplesamlphp.conf
index 190e5e9a4..9566f7bd2 100644
--- a/.docker/images/nginx/location_prepend_simplesamlphp.conf
+++ b/.docker/images/nginx/location_prepend_simplesamlphp.conf
@@ -19,3 +19,9 @@ location ~ /${LAGOON_PROJECT:-govcms}-saml/module.php/saml/sp/(saml2-logout\.php
         }
 }
 
+# Serve auto-submit JS for SAML auto-post page (HTTP-POST binding).
+location = /${LAGOON_PROJECT:-govcms}-saml/assets/base/js/post.js {
+    alias /app/vendor/simplesamlphp/simplesamlphp/public/assets/base/js/post.js;
+    access_log off;
+    expires 1h;
+}