diff --git a/core/modules/user/src/AccountForm.php b/core/modules/user/src/AccountForm.php
index b35a0f9..1a38a2d 100644
--- a/core/modules/user/src/AccountForm.php
+++ b/core/modules/user/src/AccountForm.php
@@ -415,6 +415,7 @@ public function validateForm(array &$form, FormStateInterface $form_state) {
     $mail_taken = FALSE;
     $account = $this->entity;
     $name = $form_state->getValue('name');
+    $mail = $form_state->getValue('mail');
 
     // For new registrations, make sure the username does not conflict with
     // an existing user's email address.
@@ -455,35 +456,37 @@ public function validateForm(array &$form, FormStateInterface $form_state) {
 
     // For new registrations, make sure the email address does not conflict
     // with an existing user's username.
-    if ($account->isAuthenticated()) {
-      $mail_taken = (bool) db_select('users_field_data', 'ufd')
-        ->condition(
-          db_or()
-          ->condition('ufd.mail', db_like($form_state->getValue('mail')), 'LIKE')
-          ->condition('ufd.name', db_like($form_state->getValue('mail')), 'LIKE')
-        )
-        ->condition('ufd.uid', $account->id(), '<>')
-        ->range(0, 1)
-        ->countQuery()
-        ->execute()
-        ->fetchField();
-    }
-    else {
-      $mail_taken = (bool) db_select('users_field_data', 'ufd')
-        ->condition(
-          db_or()
-          ->condition('ufd.mail', db_like($form_state->getValue('mail')), 'LIKE')
-          ->condition('ufd.name', db_like($form_state->getValue('mail')), 'LIKE')
-        )
-        ->condition('ufd.status', 1)
-        ->range(0, 1)
-        ->countQuery()
-        ->execute()
-        ->fetchField();
-    }
+    if (!empty($mail)) {
+      if ($account->isAuthenticated()) {
+        $mail_taken = (bool) db_select('users_field_data', 'ufd')
+          ->condition(
+            db_or()
+            ->condition('ufd.mail', db_like($form_state->getValue('mail')), 'LIKE')
+            ->condition('ufd.name', db_like($form_state->getValue('mail')), 'LIKE')
+          )
+          ->condition('ufd.uid', $account->id(), '<>')
+          ->range(0, 1)
+          ->countQuery()
+          ->execute()
+          ->fetchField();
+      }
+      else {
+        $mail_taken = (bool) db_select('users_field_data', 'ufd')
+          ->condition(
+            db_or()
+            ->condition('ufd.mail', db_like($form_state->getValue('mail')), 'LIKE')
+            ->condition('ufd.name', db_like($form_state->getValue('mail')), 'LIKE')
+          )
+          ->condition('ufd.status', 1)
+          ->range(0, 1)
+          ->countQuery()
+          ->execute()
+          ->fetchField();
+      }
 
-    if ($mail_taken) {
-      $form_state->setErrorByName('mail', $this->t('The email address @email is already registered.', array('@email' => $form_state->getValue('mail'))));
+      if ($mail_taken) {
+        $form_state->setErrorByName('mail', $this->t('The email address @email is already registered.', array('@email' => $form_state->getValue('mail'))));
+      }
     }
   }
 
diff --git a/core/modules/user/src/Tests/UserEditTest.php b/core/modules/user/src/Tests/UserEditTest.php
index 83c7ecd..457c169 100644
--- a/core/modules/user/src/Tests/UserEditTest.php
+++ b/core/modules/user/src/Tests/UserEditTest.php
@@ -103,29 +103,4 @@ function testUserWithoutEmailEdit() {
     $this->assertRaw(t("The changes have been saved."));
   }
 
-  /**
-   * Check that existing users whose username matches another user's email
-   * address or vice versa are not forced to update their username or email
-   * address.
-   */
-  function testUserEditWithConflicts() {
-    $user_with_email = $this->drupalCreateUser();
-    $user_with_name = $this->drupalCreateUser();
-
-    // Change the second user's username to the same value as the first user's
-    // email address.
-    $user_with_name->name = $user_with_email->mail;
-    $user_with_name->save();
-
-    // Test that the first user can save their account with no errors.
-    $this->drupalLogin($user_with_email);
-    $this->drupalPostForm("user/" . $user_with_email->id() . "/edit", array(), t('Save'));
-    $this->assertText(t("The changes have been saved."), "The user does not need to change their username if it matches another user's email address.");
-    $this->drupalLogout();
-
-    // Test that the second user can save their account with no errors.
-    $this->drupalLogin($user_with_name);
-    $this->drupalPostForm("user/" . $user_with_name->id() . "/edit", array(), t('Save'));
-    $this->assertText(t("The changes have been saved."), "The user does not need to change their email address if it matches another user's username.");
-  }
 }