diff --git a/lib/lexdee/observer.ex b/lib/lexdee/observer.ex
index e57280c..2ab6de3 100644
--- a/lib/lexdee/observer.ex
+++ b/lib/lexdee/observer.ex
@@ -59,7 +59,7 @@ defmodule Lexdee.Observer do
 
     client = Keyword.fetch!(opts, :client)
     resource = Keyword.get(opts, :resource)
-    type = Keyword.get(opts, :type, "operation")
+    type = to_string(Keyword.get(opts, :type, "operation"))
 
     %{adapter: {_, _, options}, pre: middlewares} = client
 
diff --git a/mix.exs b/mix.exs
index 15fa4bc..e14fc06 100644
--- a/mix.exs
+++ b/mix.exs
@@ -4,7 +4,7 @@ defmodule Lexdee.MixProject do
   def project do
     [
       app: :lexdee,
-      version: "2.5.0",
+      version: "2.5.1",
       elixir: "~> 1.9",
       elixirc_paths: elixirc_paths(Mix.env()),
       start_permanent: Mix.env() == :prod,