diff --git a/core/lib/Drupal/Core/Entity/Element/EntityAutocomplete.php b/core/lib/Drupal/Core/Entity/Element/EntityAutocomplete.php
index 4273a4165589348fbe720d3754ab7dc26393690d..d94e2b5fb65b7283528adee8d87f902b74702682 100644
--- a/core/lib/Drupal/Core/Entity/Element/EntityAutocomplete.php
+++ b/core/lib/Drupal/Core/Entity/Element/EntityAutocomplete.php
@@ -330,11 +330,11 @@ public static function extractEntityIdFromAutocompleteInput($input) {
 
     // Take "label (entity id)', match the ID from parenthesis when it's a
     // number.
-    if (preg_match("/.+\((\d+)\)/", $input, $matches)) {
+    if (preg_match("/.+\s\((\d+)\)/", $input, $matches)) {
       $match = $matches[1];
     }
     // Match the ID when it's a string (e.g. for config entity types).
-    elseif (preg_match("/.+\(([\w.]+)\)/", $input, $matches)) {
+    elseif (preg_match("/.+\s\(([\w.]+)\)/", $input, $matches)) {
       $match = $matches[1];
     }
 
diff --git a/core/modules/comment/src/Tests/CommentTranslationUITest.php b/core/modules/comment/src/Tests/CommentTranslationUITest.php
index 9b27a3e735fbc99a691ecfe29d63116a3e61bb3e..1246aa8d4cec080fff5efd341a31a54b8ce3d3e2 100644
--- a/core/modules/comment/src/Tests/CommentTranslationUITest.php
+++ b/core/modules/comment/src/Tests/CommentTranslationUITest.php
@@ -164,7 +164,7 @@ protected function doTestAuthoringInfo() {
         'created' => REQUEST_TIME - mt_rand(0, 1000),
       );
       $edit = array(
-        'uid' => $user->getUsername() . '(' . $user->id() . ')',
+        'uid' => $user->getUsername() . ' (' . $user->id() . ')',
         'date[date]' => format_date($values[$langcode]['created'], 'custom', 'Y-m-d'),
         'date[time]' => format_date($values[$langcode]['created'], 'custom', 'H:i:s'),
       );
diff --git a/core/modules/field/src/Tests/EntityReference/EntityReferenceAdminTest.php b/core/modules/field/src/Tests/EntityReference/EntityReferenceAdminTest.php
index 6ed4843ac3d99ab9f377037a6660341dcb4dffbc..9ee63b0732b29d1b696245db83c94b0ce097a6ff 100644
--- a/core/modules/field/src/Tests/EntityReference/EntityReferenceAdminTest.php
+++ b/core/modules/field/src/Tests/EntityReference/EntityReferenceAdminTest.php
@@ -308,7 +308,7 @@ public function testFieldAdminHandler() {
 
     $edit = array(
       'title[0][value]' => 'Test',
-      'field_test_entity_ref_field[0][target_id]' => $node1->getTitle() . '(' . $node1->id() . ')'
+      'field_test_entity_ref_field[0][target_id]' => $node1->getTitle() . ' (' . $node1->id() . ')'
     );
     $this->drupalPostForm('node/add/' . $this->type, $edit, t('Save'));
     $this->assertLink($node1->getTitle());
diff --git a/core/modules/link/src/Tests/LinkFieldTest.php b/core/modules/link/src/Tests/LinkFieldTest.php
index eada49430b2c286ad63c4e943c3a21be66f56c3c..79c2cbba5856550f342d6eeabfbbc65143456fa2 100644
--- a/core/modules/link/src/Tests/LinkFieldTest.php
+++ b/core/modules/link/src/Tests/LinkFieldTest.php
@@ -101,6 +101,10 @@ function testURLValidation() {
     // strings displayed to the user).
     $valid_external_entries = array(
       'http://www.example.com/' => 'http://www.example.com/',
+      // Strings within parenthesis without leading space char.
+      'http://www.example.com/strings_(string_within_parenthesis)' => 'http://www.example.com/strings_(string_within_parenthesis)',
+      // Numbers within parenthesis without leading space char.
+      'http://www.example.com/numbers_(9999)' => 'http://www.example.com/numbers_(9999)',
     );
     $valid_internal_entries = array(
       '/entity_test/add' => '/entity_test/add',