1 files changed, 2 insertions, 1 deletions
diff --git a/lib/Fetcher/Client/LegacyGuzzleClient.php b/lib/Fetcher/Client/LegacyGuzzleClient.php
index 4d56df0b3..59bbc9dc4 100644
--- a/lib/Fetcher/Client/LegacyGuzzleClient.php
+++ b/lib/Fetcher/Client/LegacyGuzzleClient.php
@@ -45,10 +45,11 @@ class LegacyGuzzleClient implements FeedIoClientInterface
      */
     public function getResponse(string $url, \DateTime $modifiedSince) : ResponseInterface
     {
+        $modifiedSince->setTimezone(new \DateTimeZone('GMT'));
         try {
             $options = [
                 'headers' => [
-                    'If-Modified-Since' => $modifiedSince->format(\DateTime::RFC2822)
+                    'If-Modified-Since' => $modifiedSince->format('D, d M Y H:i:s e')
                 ]
             ];