diff --git a/haskus-utils-types.cabal b/haskus-utils-types.cabal
--- a/haskus-utils-types.cabal
+++ b/haskus-utils-types.cabal
@@ -1,5 +1,5 @@
 name:                haskus-utils-types
-version:             1.5
+version:             1.5.1
 synopsis:            Haskus types utility modules
 license:             BSD3
 license-file:        LICENSE
@@ -33,7 +33,7 @@
   other-modules:
 
   build-depends:       
-         base >= 4.9 && < 5
+         base >= 4.11 && < 5
 
   ghc-options:          -Wall
   default-language:     Haskell2010
@@ -47,5 +47,5 @@
    default-language:    Haskell2010
 
    build-depends:
-         base >= 4.9 && < 5
+         base >= 4.11 && < 5
       ,  doctest >= 0.16
diff --git a/src/lib/Haskus/Utils/Types/List.hs b/src/lib/Haskus/Utils/Types/List.hs
--- a/src/lib/Haskus/Utils/Types/List.hs
+++ b/src/lib/Haskus/Utils/Types/List.hs
@@ -309,7 +309,7 @@
 type Index (n :: Nat) (l :: [k]) = Index' n l l
 
 -- | Indexed access into the list
-type family Index' (n :: Nat) (l :: [k]) (l2 :: [k]) = (r :: k) where
+type family Index' (n :: Nat) (l :: [k]) (l2 :: [k]) :: k where
    Index' 0 (x ': _ ) _  = x
    Index' n (_ ': xs) l2 = Index' (n-1) xs l2
    Index' n '[]       l2 = TypeError ( 'Text "Index "