diff --git a/exam/ex.tex b/exam/ex.tex
index ac36f7b..c1e6686 100644
--- a/exam/ex.tex
+++ b/exam/ex.tex
@@ -297,8 +297,9 @@
       commitment phase takes the isomorphism $\psi$ and the graph $\mathcal{G}$
       as input and produces a commitment $\mathcal{G}'$. The opening phase takes
       an isomorphism $\mathsf{resp}$ and another graph
-      $\mathcal{G}_{\mathsf{ch}}$ isomorphic to $\mathcal{G}$ as input and
-      outputs $\top$ if the result matches $\mathcal{G}'$ and $\bot$ otherwise.
+      $\mathcal{G}_{\mathsf{ch}}$ isomorphic to $\mathcal{G}$ as well as the
+      original commitment as input and outputs $\top$ if the result matches
+      $\mathcal{G}'$ and $\bot$ otherwise.
 
     \item Computational binding: Suppose $\mathsf{Comm}(\psi,\mathcal{G}_0) =
       \mathsf{Comm}(\psi,\mathcal{G}_1)$. This means that $\psi(\mathcal{G}_0) =