diff --git a/transformations/SimplifyExprs.hs b/transformations/SimplifyExprs.hs
index 0177f34..d501e18 100644
--- a/transformations/SimplifyExprs.hs
+++ b/transformations/SimplifyExprs.hs
@@ -222,6 +222,7 @@ pullUp = doGeneric
                   case e' of
                     A.ExprVariable _ (A.Variable _ _) -> return e'
                     A.ExprVariable _ (A.DirectedVariable _ _ _) -> return e'
+                    --TODO work out whether to pull up DerefVariable
                     _ -> pull t e'
                 _ -> return e'
       where