diff --git a/src/Fedi/Signature/Sign.hs b/src/Fedi/Signature/Sign.hs
index 9f0c663..2b1e079 100644
--- a/src/Fedi/Signature/Sign.hs
+++ b/src/Fedi/Signature/Sign.hs
@@ -20,7 +20,7 @@ signSignature
   :: UserDetails -> String -> String -> ByteString -> IO HttpSignature
 signSignature details host requestTarget body = do
   date <- Time.getCurrentTime
-    <&> Time.formatTime Time.defaultTimeLocale Time.rfc822DateFormat
+    <&> Time.formatTime Time.defaultTimeLocale "%a, %d %b %Y %H:%M:%S GMT"
 
   let
     digest = "SHA-256=" <> encodeBase64 (makeDigest body)