diff --git a/src/CPS.ml b/src/CPS.ml
index 77eaca0..0714e87 100644
--- a/src/CPS.ml
+++ b/src/CPS.ml
@@ -6,6 +6,8 @@ module T = Tail
 exception NotValue of S.term
 (** ^ Raised when trying to use a non-value term as such *)
 
+exception NotLightCPSable of S.term
+
 let freshId =
     (** Generates a fresh variable name string *)
     let cId = ref 0 in
@@ -113,7 +115,8 @@ and light_term varName valExpr valHint next =
                         self, [lamVar; lamCont],
                         cps_term_inner lamBody lamCont None),
                     next)
-        | S.App _ | S.Print _ | S.IfZero _ -> assert false
+        | S.App _ | S.Print _ | S.IfZero _ ->
+                raise (NotLightCPSable valExpr)
     )