diff --git a/3or4/Interpreter/Self.hs b/3or4/Interpreter/Self.hs
index b09ea02..0ff6951 100644
--- a/3or4/Interpreter/Self.hs
+++ b/3or4/Interpreter/Self.hs
@@ -70,7 +70,7 @@ lookupExp =
   \ -- TODO: Fix for Nil() \
   \ { Cons(b,bs) -> \
   \     case b of \
-  \       { Branch(c', bs, e') -> if (equal c c') Pair(bs,e') (lookup bs) } \
+  \       { Branch(c', xs, e') -> if (equal c c') Pair(xs,e') (lookup bs) } \
   \ }"
 
 substsExp :: Exp