diff --git a/src/Handler/Utils/Submission.hs b/src/Handler/Utils/Submission.hs
index a397041a8..124da1b83 100644
--- a/src/Handler/Utils/Submission.hs
+++ b/src/Handler/Utils/Submission.hs
@@ -130,7 +130,9 @@ assignSubmissions sid restriction = do
           props = getSum $ foldMap (Sum . fst) assignments
 
           toDeficit' (prop, assigned) = let
-              target = round $ fromInteger assigned' * (prop / props)
+              target
+                | props == 0 = 0
+                | otherwise  = round $ fromInteger assigned' * (prop / props)
             in target - assigned
 
     $logDebugS "assignSubmissions" $ "Previous submissions: " <> tshow prevSubs'