diff --git a/lib/surface/formatter/phases/render.ex b/lib/surface/formatter/phases/render.ex
index 5b5a9c3..0eebc61 100644
--- a/lib/surface/formatter/phases/render.ex
+++ b/lib/surface/formatter/phases/render.ex
@@ -130,7 +130,7 @@ defmodule Surface.Formatter.Phases.Render do
 
             string ->
               string
-              |> String.slice(1..-2)
+              |> String.slice(1..-2//1)
               |> String.trim()
           end