diff --git a/src/Handler/Utils/Course.hs b/src/Handler/Utils/Course.hs
index 699f96aa5..a595c37ca 100644
--- a/src/Handler/Utils/Course.hs
+++ b/src/Handler/Utils/Course.hs
@@ -64,6 +64,7 @@ setUsersSubmissionGroup cid uids (Just grp) = do
   E.delete . E.from $ \submissionGroup ->
     E.where_ $ submissionGroup E.^. SubmissionGroupCourse E.==. E.val cid
          E.&&. E.not_ (E.exists . E.from $ \submissionGroupUser -> E.where_ $ submissionGroupUser E.^. SubmissionGroupUserSubmissionGroup E.==. submissionGroup E.^. SubmissionGroupId)
+         E.&&. submissionGroup E.^. SubmissionGroupId E.!=. E.val gId
   fmap getSum . flip foldMapM uids $ \uid -> do
     didSet <- fmap (is _Just) . insertUnique $ SubmissionGroupUser gId uid
     when didSet $