diff --git a/lib/Newsletter/Renderer/Blocks/Footer.php b/lib/Newsletter/Renderer/Blocks/Footer.php
index e410480227..e44cac4b81 100644
--- a/lib/Newsletter/Renderer/Blocks/Footer.php
+++ b/lib/Newsletter/Renderer/Blocks/Footer.php
@@ -14,6 +14,9 @@ class Footer {
     $lineHeight = sprintf(
       '%spx', StylesHelper::$defaultLineHeight * (int)$element['styles']['text']['fontSize']
     );
+    if (!is_string($element['text'])) {
+      throw new \RuntimeException('$element[\'text\'] should be a string.');
+    }
     $dOMParser = new pQuery();
     $DOM = $dOMParser->parseStr($element['text']);
     if (isset($element['styles']['link'])) {
diff --git a/lib/Newsletter/Renderer/Blocks/Header.php b/lib/Newsletter/Renderer/Blocks/Header.php
index 93d266ec9e..cb3eda3f95 100644
--- a/lib/Newsletter/Renderer/Blocks/Header.php
+++ b/lib/Newsletter/Renderer/Blocks/Header.php
@@ -14,6 +14,9 @@ class Header {
     $lineHeight = sprintf(
       '%spx', StylesHelper::$defaultLineHeight * (int)$element['styles']['text']['fontSize']
     );
+    if (!is_string($element['text'])) {
+      throw new \RuntimeException('$element[\'text\'] should be a string.');
+    }
     $dOMParser = new pQuery();
     $DOM = $dOMParser->parseStr($element['text']);
     if (isset($element['styles']['link'])) {
diff --git a/tests/unit/Newsletter/Renderer/Blocks/FooterTest.php b/tests/unit/Newsletter/Renderer/Blocks/FooterTest.php
index 9d80e5c3ab..1298dd5d7b 100644
--- a/tests/unit/Newsletter/Renderer/Blocks/FooterTest.php
+++ b/tests/unit/Newsletter/Renderer/Blocks/FooterTest.php
@@ -52,4 +52,10 @@ class FooterTest extends \MailPoetUnitTest {
     $output = (new Footer)->render($this->block);
     expect($output)->stringContainsString('<a href="http://example.com" style="color:#aaaaaa;text-decoration:none">link</a>');
   }
+
+  public function testItRaisesExceptionIfTextIsNotString() {
+    $this->block['text'] = ['some', 'array'];
+    $this->expectException('RuntimeException');
+    (new Footer)->render($this->block);
+  }
 }
diff --git a/tests/unit/Newsletter/Renderer/Blocks/HeaderTest.php b/tests/unit/Newsletter/Renderer/Blocks/HeaderTest.php
index 79090b29f3..12e6051f31 100644
--- a/tests/unit/Newsletter/Renderer/Blocks/HeaderTest.php
+++ b/tests/unit/Newsletter/Renderer/Blocks/HeaderTest.php
@@ -52,4 +52,10 @@ class HeaderTest extends \MailPoetUnitTest {
     $output = (new Footer)->render($this->block);
     expect($output)->stringContainsString('<a href="http://example.com" style="color:#aaaaaa;text-decoration:underline">link</a>');
   }
+
+  public function testItRaisesExceptionIfTextIsNotString() {
+    $this->block['text'] = ['some', 'array'];
+    $this->expectException('RuntimeException');
+    (new Header)->render($this->block);
+  }
 }