diff --git a/src/content/2.4/representable-functors.tex b/src/content/2.4/representable-functors.tex
index f792a485..0a6b8028 100644
--- a/src/content/2.4/representable-functors.tex
+++ b/src/content/2.4/representable-functors.tex
@@ -315,7 +315,7 @@ \section{Challenges}
         The functor:
 
         \begin{snip}{haskell}
-Pair a = Pair a a
+data Pair a = Pair a a
 \end{snip}
         is representable. Can you guess the type that represents it? Implement
         \code{tabulate} and \code{index}.