diff --git a/core/lib/Drupal/Core/Composer/ExtensionDependencyChecker.php b/core/lib/Drupal/Core/Composer/ExtensionDependencyChecker.php
index f26d40b..d3813ef 100644
--- a/core/lib/Drupal/Core/Composer/ExtensionDependencyChecker.php
+++ b/core/lib/Drupal/Core/Composer/ExtensionDependencyChecker.php
@@ -9,15 +9,12 @@
 
 use Composer\Semver\Semver;
 use Drupal\Core\Extension\Extension;
-use Drupal\Core\StringTranslation\StringTranslationTrait;
 
 /**
  * Performs a naive check for Composer-based module dependencies.
  */
 class ExtensionDependencyChecker {
 
-  use StringTranslationTrait;
-
   /**
    * The path to the Drupal root directory.
    *
@@ -28,13 +25,14 @@ class ExtensionDependencyChecker {
   /**
    * The Composer packages that are currently installed.
    *
-   * We store this so the object is re-usable without re-parsing the file.
+   * @see self::getInstalledPackages()
    *
-   * @var string[]
-   *   Keys are package names and values are package versions. Example:
-   *   ['crell/api-problem' => '1.7.0'.\].
+   * @var null|string[]
+   *   Either NULL when the installed packages have not been computed yet, or an
+   *   array of which keys are package names and values are package versions.
+   *   Example: ['crell/api-problem' => '1.7.0'].
    */
-  protected $composerInstalled = [];
+  protected $installedPackages;
 
   /**
    * Creates a new instance.
@@ -56,30 +54,35 @@ public function __construct($drupal_root) {
    *   TRUE if this extension's Composer dependencies are met, FALSE otherwise.
    */
   public function dependenciesAreMet(Extension $extension) {
-    // Does the extension have a composer.json file?
     $composer_file_path = $this->drupalRoot . '/' . $extension->getPath() . '/composer.json';
-    if (is_readable($composer_file_path)) {
-      $composer_dependencies = json_decode(file_get_contents($composer_file_path));
-      $installed_packages = $this->getInstalledPackages();
-
-      // Gather all the requirements.
-      $require = [];
-      if (!empty($composer_dependencies->require)) {
-        $require = (array) $composer_dependencies->require;
+
+    // If the extension has on Composer file, it has no unmet dependencies.
+    if (!file_exists($composer_file_path)) {
+      return TRUE;
+    }
+
+    $composer_file = json_decode(file_get_contents($composer_file_path));
+
+    // If the extension has no Composer dependencies at all, it has no unmet
+    // dependencies.
+    if (empty($composer_file->require)) {
+      return TRUE;
+    }
+
+    $requirements = (array) $composer_file->require;
+    $installed_packages = $this->getInstalledPackages();
+    $semver = new Semver();
+
+    // Check each required package against the list of installed packages.
+    foreach ($requirements as $package_name => $constraint) {
+      // If a dependency is not installed at all, it is unmet.
+      if (empty($installed_packages[$package_name])) {
+        return FALSE;
       }
-      if (!empty($require)) {
-        // Check each required package against the list of installed packages.
-        $semver = new Semver();
-        foreach ($require as $package_name => $constraint) {
-          if (empty($installed_packages[$package_name])) {
-            return FALSE;
-          }
-          if (!$semver->satisfies($installed_packages[$package_name], $constraint)) {
-            return FALSE;
-          }
-        }
+      // If the wrong version of a dependency is installed, it is unmet.
+      elseif (!$semver->satisfies($installed_packages[$package_name], $constraint)) {
+        return FALSE;
       }
-      return TRUE;
     }
     return TRUE;
   }
@@ -89,22 +92,31 @@ public function dependenciesAreMet(Extension $extension) {
    *
    * @return string[]
    *   Keys are package names and values are package versions. Example:
-   *   ['crell/api-problem' => '1.7.0'.\].
+   *   ['crell/api-problem' => '1.7.0'].
    */
   protected function getInstalledPackages() {
-    // Find the installed packages once, and cache the data.
-    if (empty($this->composerInstalled)) {
-      $installed_json = $this->drupalRoot . '/vendor/composer/installed.json';
-      if (file_exists($installed_json)) {
-        $json = file_get_contents($installed_json, FALSE);
-        foreach (json_decode($json) as $package) {
-          if (isset($package->name) && isset($package->version_normalized)) {
-            $this->composerInstalled[$package->name] = $package->version_normalized;
-          }
-        }
+    // Quickly return the cached list, if it exists.
+    if (is_array($this->installedPackages)) {
+      return $this->installedPackages;
+    }
+
+    $installed_json_path = $this->drupalRoot . '/vendor/composer/installed.json';
+
+    // If installed.json does not exist, no packages are installed.
+    if (!file_exists($installed_json_path)) {
+      $this->installedPackages = [];
+      return $this->installedPackages;
+    }
+
+    // Parse the list once and then cache it.
+    $json = file_get_contents($installed_json_path, FALSE);
+    $this->installedPackages = [];
+    foreach (json_decode($json) as $package) {
+      if (isset($package->name) && isset($package->version_normalized)) {
+        $this->installedPackages[$package->name] = $package->version_normalized;
       }
     }
-    return $this->composerInstalled;
+    return $this->installedPackages;
   }
 
 }