diff --git a/src/TwigExtension.php b/src/TwigExtension.php
index 4ccbfc0..fd54657 100644
--- a/src/TwigExtension.php
+++ b/src/TwigExtension.php
@@ -486,7 +486,7 @@ class TwigExtension extends AbstractExtension {
       $build['content']['#cache']['contexts'][] = 'url';
     }
 
-    if ($wrapper && !Element::isEmpty($build['content'])) {
+    if ($wrapper && is_array($build['content']) && !Element::isEmpty($build['content'])) {
       $build += [
         '#theme' => 'block',
         '#id' => $configuration['id'] ?? NULL,