diff --git a/core/lib/Drupal/Core/Updater/Module.php b/core/lib/Drupal/Core/Updater/Module.php
index acc3028..daab4f1 100644
--- a/core/lib/Drupal/Core/Updater/Module.php
+++ b/core/lib/Drupal/Core/Updater/Module.php
@@ -49,10 +49,9 @@ public function isInstalled() {
    * Implements Drupal\Core\Updater\UpdaterInterface::canUpdateDirectory().
    */
   public static function canUpdateDirectory($directory) {
-    if (file_scan_directory($directory, '/.*\.module$/')) {
-      return TRUE;
-    }
-    return FALSE;
+    $files = file_scan_directory($directory, '/.*\.info\.yml$/');
+    $info = drupal_parse_info_file(reset($files)->uri);
+    return $info['type'] == 'module';
   }
 
   /**
diff --git a/core/lib/Drupal/Core/Updater/Theme.php b/core/lib/Drupal/Core/Updater/Theme.php
index 9770ab9..3f02b0d 100644
--- a/core/lib/Drupal/Core/Updater/Theme.php
+++ b/core/lib/Drupal/Core/Updater/Theme.php
@@ -49,11 +49,9 @@ public function isInstalled() {
    * Implements Drupal\Core\Updater\UpdaterInterface::canUpdateDirectory().
    */
   static function canUpdateDirectory($directory) {
-    // This is a lousy test, but don't know how else to confirm it is a theme.
-    if (file_scan_directory($directory, '/.*\.theme$/')) {
-      return FALSE;
-    }
-    return TRUE;
+    $files = file_scan_directory($directory, '/.*\.info\.yml$/');
+    $info = drupal_parse_info_file(reset($files)->uri);
+    return $info['type'] == 'theme';
   }
 
   /**