diff --git a/core/lib/Drupal/Core/Diff/DiffFormatter.php b/core/lib/Drupal/Core/Diff/DiffFormatter.php
index 0e59e88..b05133c 100644
--- a/core/lib/Drupal/Core/Diff/DiffFormatter.php
+++ b/core/lib/Drupal/Core/Diff/DiffFormatter.php
@@ -9,6 +9,7 @@
 
 use Drupal\Component\Diff\DiffFormatter as DiffFormatterBase;
 use Drupal\Component\Diff\WordLevelDiff;
+use Drupal\Component\Utility\SafeMarkup;
 use Drupal\Component\Utility\String;
 use Drupal\Core\Config\ConfigFactoryInterface;
 
@@ -146,11 +147,11 @@ protected function deletedLine($line) {
    */
   protected function contextLine($line) {
     return array(
-      ' ',
+      SafeMarkup::set(' '),
       array(
         'data' => $line,
         'class' => 'diff-context',
-      )
+      ),
     );
   }
 
diff --git a/core/modules/config/src/Tests/ConfigImportUITest.php b/core/modules/config/src/Tests/ConfigImportUITest.php
index 1c301d6..c07f892 100644
--- a/core/modules/config/src/Tests/ConfigImportUITest.php
+++ b/core/modules/config/src/Tests/ConfigImportUITest.php
@@ -281,6 +281,7 @@ function testImportDiff() {
 
     // Load the diff UI and verify that the diff reflects the change.
     $this->drupalGet('admin/config/development/configuration/sync/diff/' . $config_name);
+    $this->assertNoRaw(' ');
     $this->assertTitle(format_string('View changes of @config_name | Drupal', array('@config_name' => $config_name)));
 
     // Reset data back to original, and remove a key