diff --git a/src/CryptoID.hs b/src/CryptoID.hs
index 3720c461b..5eda0a941 100644
--- a/src/CryptoID.hs
+++ b/src/CryptoID.hs
@@ -40,6 +40,7 @@ decCryptoIDs [ ''SubmissionId
              , ''CourseId
              , ''SheetId
              , ''FileId
+             , ''UserId
              ]
 {- TODO: Do we need/want CryptoUUIDs for Sheet numbers? -}