diff --git a/src/CPS.ml b/src/CPS.ml
index bab67e6..9a5c0d6 100644
--- a/src/CPS.ml
+++ b/src/CPS.ml
@@ -3,7 +3,8 @@ module S = Lambda
 (* The target calculus. *)
 module T = Tail
 
-exception NotValue (** <- Raised when trying to use a non-value term as such *)
+exception NotValue of S.term
+(** ^ Raised when trying to use a non-value term as such *)
 
 let freshId =
     (** Generates a fresh variable name string *)
@@ -30,7 +31,7 @@ let rec cps_value (t: S.term) : T.value = match t with
 | S.Var v -> T.VVar v
 | S.Lit v -> T.VLit v
 | S.BinOp (l, op, r) -> T.VBinOp (cps_value l, op, cps_value r)
-| S.Let _ | S.Lam _ | S.App _ | S.Print _ | S.IfZero _ -> raise NotValue
+| S.Let _ | S.Lam _ | S.App _ | S.Print _ | S.IfZero _ -> raise (NotValue t)
 
 let cps_value_as_term (t: S.term) (cont: T.variable): T.term =
     T.TailCall(T.vvar cont, [cps_value t])