diff --git a/core/lib/Drupal/Core/StringTranslation/PluralTranslatableMarkup.php b/core/lib/Drupal/Core/StringTranslation/PluralTranslatableMarkup.php
index 6c1d4c9..80365ad 100644
--- a/core/lib/Drupal/Core/StringTranslation/PluralTranslatableMarkup.php
+++ b/core/lib/Drupal/Core/StringTranslation/PluralTranslatableMarkup.php
@@ -150,7 +150,13 @@ public function render() {
    * @return int
    */
   protected function getPluralIndex() {
-    if (function_exists('locale_get_plural')) {
+    // We have to test both if the function exists and the service since in certain
+    // certain situations it is possible that locale code might be loaded but
+    // the service does not exist. For example, where the parent test site has
+    // locale installed but the child site does not.
+    // @todo Refactor in https://www.drupal.org/node/2660338 so this code does
+    //   not depend on knowing that the Locale module exists.
+    if (function_exists('locale_get_plural') && \Drupal::hasService('locale.plural.formula')) {
       return locale_get_plural($this->count, $this->getOption('langcode'));
     }
     return -1;
diff --git a/core/modules/locale/locale.module b/core/modules/locale/locale.module
index f9f5226..74b76ec 100644
--- a/core/modules/locale/locale.module
+++ b/core/modules/locale/locale.module
@@ -283,9 +283,7 @@ function locale_get_plural($count, $langcode = NULL) {
 
   if (!isset($plural_indexes[$langcode][$count])) {
     // Retrieve and statically cache the plural formulas for all languages.
-    if (\Drupal::hasService('locale.plural.formula')) {
-      $plural_formulas = \Drupal::service('locale.plural.formula')->getFormula($langcode);
-    }
+    $plural_formulas = \Drupal::service('locale.plural.formula')->getFormula($langcode);
 
     // If there is a plural formula for the language, evaluate it for the given
     // $count and statically cache the result for the combination of language