diff --git a/src/CPS.ml b/src/CPS.ml
index 017204e..2eb974c 100644
--- a/src/CPS.ml
+++ b/src/CPS.ml
@@ -13,7 +13,7 @@ let freshId =
         (string_of_int !cId))
 
 let freshWithPrefix pre =
-    Atom.fresh (pre ^ (freshId ()))
+    Atom.fresh (pre ^ (freshId ()) ^ "_")
 let freshBlockVar () = freshWithPrefix "bl_"
 let freshVar () = freshWithPrefix "v_"