diff --git a/serversession-backend-redis/src/Web/ServerSession/Backend/Redis/Internal.hs b/serversession-backend-redis/src/Web/ServerSession/Backend/Redis/Internal.hs
index 291a209..88f2a35 100644
--- a/serversession-backend-redis/src/Web/ServerSession/Backend/Redis/Internal.hs
+++ b/serversession-backend-redis/src/Web/ServerSession/Backend/Redis/Internal.hs
@@ -158,7 +158,7 @@ printUTCTime = B8.pack . TI.formatTime TI.defaultTimeLocale timeFormat
 
 -- | Time format used when storing 'UTCTime'.
 timeFormat :: String
-timeFormat = "%Y-%m-%dT%H:%M:%S"
+timeFormat = "%Y-%m-%dT%H:%M:%S.%q"
 
 
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