diff --git a/code/GADTs.hs b/code/GADTs.hs
index 4ca0ace..a00c93f 100644
--- a/code/GADTs.hs
+++ b/code/GADTs.hs
@@ -94,7 +94,7 @@ instance Show (HList '[]) where
 -- # showHCons
 instance (Show t, Show (HList ts))
     => Show (HList (t ': ts)) where
-  show (a :# as) = show a <> " :# " show as
+  show (a :# as) = show a <> " :# " <> show as
 
 -}
 
diff --git a/gadts.tex b/gadts.tex
index edbcb13..442c87f 100644
--- a/gadts.tex
+++ b/gadts.tex
@@ -268,6 +268,8 @@ \section{Heterogeneous Lists}
 
 \begin{exercise}
 Rewrite the \ty{Ord} and \ty{Show} instances in terms of \ty{All}.
+Hint: your instance for \ty{Eq} needs to be implementend in terms of \ty{All}
+as well.
 \end{exercise}
 \begin{solution}
 \unspacedSnip{GADTs}{ordHList}