diff --git a/plugins/password/drivers/httpapi.php b/plugins/password/drivers/httpapi.php
index 2bcacd65a..3835a8f19 100644
--- a/plugins/password/drivers/httpapi.php
+++ b/plugins/password/drivers/httpapi.php
@@ -113,7 +113,7 @@ class rcube_httpapi_password
         if ($response_code < 200 || $response_code > 299) {
             rcube::raise_error([
                     'code' => 600, 'file' => __FILE__, 'line' => __LINE__,
-                    'message' => "Password plugin: Unexpected response code ${response_code}: "
+                    'message' => "Password plugin: Unexpected response code {$response_code}: "
                         . substr($result, 0, 1024)
                 ],
                 true, false
diff --git a/plugins/password/tests/Password.php b/plugins/password/tests/Password.php
index 17d18ec5b..ba5fe6552 100644
--- a/plugins/password/tests/Password.php
+++ b/plugins/password/tests/Password.php
@@ -83,7 +83,7 @@ class Password_Plugin extends PHPUnit\Framework\TestCase
     function load_driver($driver)
     {
         include_once __DIR__ . "/../drivers/$driver.php";
-        $driver_class = "rcube_${driver}_password";
+        $driver_class = "rcube_{$driver}_password";
         $this->assertTrue(class_exists($driver_class));
         return $driver_class;
     }