diff --git a/core/modules/language/src/Tests/LanguageUILanguageNegotiationTest.php b/core/modules/language/src/Tests/LanguageUILanguageNegotiationTest.php
index 6a81438..4b2c3d3 100644
--- a/core/modules/language/src/Tests/LanguageUILanguageNegotiationTest.php
+++ b/core/modules/language/src/Tests/LanguageUILanguageNegotiationTest.php
@@ -391,6 +391,11 @@ function testUrlLanguageFallback() {
    * Tests _url() when separate domains are used for multiple languages.
    */
   function testLanguageDomain() {
+    global $base_url;
+
+    // Getting the current host URI we're running on.
+    $base_url_host = parse_url($base_url, PHP_URL_HOST);
+
     // Add the Italian language.
     ConfigurableLanguage::createFromLangcode('it')->save();
 
@@ -415,7 +420,7 @@ function testLanguageDomain() {
     // Change the domain for the Italian language.
     $edit = array(
       'language_negotiation_url_part' => LanguageNegotiationUrl::CONFIG_DOMAIN,
-      'domain[en]' => gethostname(),
+      'domain[en]' => $base_url_host,
       'domain[it]' => 'it.example.com',
     );
     $this->drupalPostForm('admin/config/regional/language/detection/url', $edit, t('Save configuration'));
diff --git a/core/modules/language/src/Tests/LanguageUrlRewritingTest.php b/core/modules/language/src/Tests/LanguageUrlRewritingTest.php
index 0d4c2ce..344b3b8 100644
--- a/core/modules/language/src/Tests/LanguageUrlRewritingTest.php
+++ b/core/modules/language/src/Tests/LanguageUrlRewritingTest.php
@@ -98,10 +98,13 @@ private function checkUrl($language, $message1, $message2) {
    * Check URL rewriting when using a domain name and a non-standard port.
    */
   function testDomainNameNegotiationPort() {
+    global $base_url;
     $language_domain = 'example.fr';
+    // Getting the current host URI we're running on.
+    $base_url_host = parse_url($base_url, PHP_URL_HOST);
     $edit = array(
       'language_negotiation_url_part' => LanguageNegotiationUrl::CONFIG_DOMAIN,
-      'domain[en]' => gethostname(),
+      'domain[en]' => $base_url_host,
       'domain[fr]' => $language_domain
     );
     $this->drupalPostForm('admin/config/regional/language/detection/url', $edit, t('Save configuration'));