diff --git a/src/Model/Types/Sheet.hs b/src/Model/Types/Sheet.hs
index 5760233eb..e4821cf73 100644
--- a/src/Model/Types/Sheet.hs
+++ b/src/Model/Types/Sheet.hs
@@ -91,10 +91,9 @@ data SheetGradeSummary = SheetGradeSummary
 
 instance Monoid SheetGradeSummary where
   mempty  = memptydefault
-  mappend = mappenddefault
 
 instance Semigroup SheetGradeSummary where
-  (<>) = mappend -- TODO: remove for GHC > 8.4.x
+  (<>) = mappenddefault
 
 makeLenses_ ''SheetGradeSummary
 
@@ -155,10 +154,9 @@ data SheetTypeSummary exampartid = SheetTypeSummary
 
 instance Ord epid => Monoid (SheetTypeSummary epid) where
   mempty  = memptydefault
-  mappend = mappenddefault
 
 instance Ord epid => Semigroup (SheetTypeSummary epid) where
-  (<>) = mappend -- TODO: remove for GHC > 8.4.x
+  (<>) = mappenddefault
 
 makeLenses_ ''SheetTypeSummary