diff --git a/core/modules/filter/src/Plugin/Filter/FilterHtml.php b/core/modules/filter/src/Plugin/Filter/FilterHtml.php
index 1dc3395161a..1dc71fba01e 100644
--- a/core/modules/filter/src/Plugin/Filter/FilterHtml.php
+++ b/core/modules/filter/src/Plugin/Filter/FilterHtml.php
@@ -41,12 +41,10 @@ class FilterHtml extends FilterBase {
    */
   public function settingsForm(array $form, FormStateInterface $form_state) {
     $form['allowed_html'] = array(
-      '#type' => 'textfield',
+      '#type' => 'textarea',
       '#title' => $this->t('Allowed HTML tags'),
       '#default_value' => $this->settings['allowed_html'],
-      '#maxlength' => 2048,
       '#description' => $this->t('A list of HTML tags that can be used. By default only the <em>lang</em> and <em>dir</em> attributes are allowed for all HTML tags. Each HTML tag may have attributes which are treated as allowed attribute names for that HTML tag. Each attribute may allow all values, or only allow specific values. Attribute names or values may be written as a prefix and wildcard like <em>jump-*</em>. JavaScript event attributes, JavaScript URLs, and CSS are always stripped.'),
-      '#size' => 250,
       '#attached' => array(
         'library' => array(
           'filter/drupal.filter.filter_html.admin',
@@ -70,6 +68,12 @@ class FilterHtml extends FilterBase {
    * {@inheritdoc}
    */
   public function setConfiguration(array $configuration) {
+    if (isset($configuration['settings']['allowed_html'])) {
+      // The javascript in core/modules/filter/filter.filter_html.admin.js
+      // removes new lines and double spaces so, for consistency when javascript
+      // is disabled, remove them.
+      $configuration['settings']['allowed_html'] = preg_replace('/\s+/', ' ', $configuration['settings']['allowed_html']);
+    }
     parent::setConfiguration($configuration);
     // Force restrictions to be calculated again.
     $this->restrictions = NULL;
diff --git a/core/modules/filter/src/Tests/FilterAdminTest.php b/core/modules/filter/src/Tests/FilterAdminTest.php
index e71b57ab45c..830cf18d776 100644
--- a/core/modules/filter/src/Tests/FilterAdminTest.php
+++ b/core/modules/filter/src/Tests/FilterAdminTest.php
@@ -206,13 +206,13 @@ class FilterAdminTest extends WebTestBase {
     $this->assertTrue($full_format->access('use', $this->adminUser), 'Admin user may use Full HTML.');
     $this->assertFalse($full_format->access('use', $this->webUser), 'Web user may not use Full HTML.');
 
-    // Add an additional tag.
+    // Add an additional tag and extra spaces and returns.
     $edit = array();
-    $edit['filters[filter_html][settings][allowed_html]'] = '<a> <em> <strong> <cite> <code> <ul> <ol> <li> <dl> <dt> <dd> <quote>';
+    $edit['filters[filter_html][settings][allowed_html]'] = "<a>   <em> <strong> <cite> <code> <ul> <ol> <li> <dl> <dt> <dd>\r\n<quote>";
     $this->drupalPostForm('admin/config/content/formats/manage/' . $restricted, $edit, t('Save configuration'));
     $this->assertUrl('admin/config/content/formats');
     $this->drupalGet('admin/config/content/formats/manage/' . $restricted);
-    $this->assertFieldByName('filters[filter_html][settings][allowed_html]', $edit['filters[filter_html][settings][allowed_html]'], 'Allowed HTML tag added.');
+    $this->assertFieldByName('filters[filter_html][settings][allowed_html]', "<a> <em> <strong> <cite> <code> <ul> <ol> <li> <dl> <dt> <dd> <quote>", 'Allowed HTML tag added.');
 
     $elements = $this->xpath('//select[@name=:first]/following::select[@name=:second]', array(
       ':first' => 'filters[' . $first_filter . '][weight]',
diff --git a/core/modules/filter/tests/src/Unit/FilterHtmlTest.php b/core/modules/filter/tests/src/Unit/FilterHtmlTest.php
index a3cde04e96d..664c2a3001a 100644
--- a/core/modules/filter/tests/src/Unit/FilterHtmlTest.php
+++ b/core/modules/filter/tests/src/Unit/FilterHtmlTest.php
@@ -79,4 +79,18 @@ class FilterHtmlTest extends UnitTestCase {
     ];
   }
 
+  /**
+   * @covers ::setConfiguration
+   */
+  public function testSetConfiguration() {
+    $configuration['settings'] = [
+      // New lines and spaces are replaced with a single space.
+      'allowed_html' => "<a>  <br>\r\n  <p>",
+      'filter_html_help' => 1,
+      'filter_html_nofollow' => 0,
+    ];
+    $filter = new FilterHtml($configuration, 'filter_html', ['provider' => 'test']);
+    $this->assertSame('<a> <br> <p>', $filter->getConfiguration()['settings']['allowed_html']);
+  }
+
 }