diff --git a/aspecs/lib/Asterix/Specs/Types.hs b/aspecs/lib/Asterix/Specs/Types.hs
index 4a529db..b4fee38 100644
--- a/aspecs/lib/Asterix/Specs/Types.hs
+++ b/aspecs/lib/Asterix/Specs/Types.hs
@@ -11,9 +11,15 @@ newtype CatNum = CatNum Int
 newtype BitSize = BitSize Int
     deriving (Generic, Eq, Ord, Show, Read)
 
+instance Semigroup BitSize where BitSize a <> BitSize b = BitSize (a+b)
+instance Monoid BitSize where mempty = BitSize 0
+
 newtype ByteSize = ByteSize Int
     deriving (Generic, Eq, Ord, Show, Read)
 
+instance Semigroup ByteSize where ByteSize a <> ByteSize b = ByteSize (a+b)
+instance Monoid ByteSize where mempty = ByteSize 0
+
 newtype ItemName = ItemName Text
     deriving (Generic, Eq, Ord, Show, Read)
 
diff --git a/aspecs/lib/Asterix/Specs/Validation.hs b/aspecs/lib/Asterix/Specs/Validation.hs
index 33f352a..f5a021c 100644
--- a/aspecs/lib/Asterix/Specs/Validation.hs
+++ b/aspecs/lib/Asterix/Specs/Validation.hs
@@ -204,7 +204,7 @@ catUapItems = mapMaybe f where
         UapItem name -> Just name
         _ -> Nothing
 
-instance Validate ([Item ()], (Uap [UapItem ItemName])) where
+instance Validate ([Item ()], Uap [UapItem ItemName]) where
     validate (catalogue, uap) = case uap of
         Uap lst -> validateList lst
         Uaps lst1 msel -> do