diff --git a/core/includes/bootstrap.inc b/core/includes/bootstrap.inc
index d58779d..9e4f25d 100644
--- a/core/includes/bootstrap.inc
+++ b/core/includes/bootstrap.inc
@@ -701,7 +701,8 @@ function drupal_generate_test_ua($prefix) {
   if (!isset($key) || $last_prefix != $prefix) {
     $last_prefix = $prefix;
     $test_db = new TestDatabase($prefix);
-    $key_file = DRUPAL_ROOT . '/' . $test_db->getTestSitePath() . '/.htkey';
+    $key_file_directory = DRUPAL_ROOT . '/' . $test_db->getTestSitePath();
+    $key_file = $key_file_directory . '/.htkey';
     // When issuing an outbound HTTP client request from within an inbound test
     // request, then the outbound request has to use the same User-Agent header
     // as the inbound request. A newly generated private key for the same test
@@ -717,6 +718,7 @@ function drupal_generate_test_ua($prefix) {
     else {
       // Generate and save a new hash salt for a test run.
       // Consumed by drupal_valid_test_ua() before settings.php is loaded.
+      file_exists($key_file_directory) ? chmod($key_file_directory, 0775) : mkdir($key_file_directory, 0755);
       $private_key = Crypt::randomBytesBase64(55);
       file_put_contents($key_file, $private_key);
     }