diff --git a/config/dev.exs b/config/dev.exs
index ce285cd..033d696 100644
--- a/config/dev.exs
+++ b/config/dev.exs
@@ -4,4 +4,5 @@ config :elixir_authorizenet,
   environment: :production,
   validation_mode: :live, # :test, :live, or :none
   login_id: "login_id",
-  transaction_key: "transaction_key"
+  transaction_key: "transaction_key",
+  mix_env: :dev
diff --git a/config/dev.exs.sample b/config/dev.exs.sample
index f15d696..72a8650 100644
--- a/config/dev.exs.sample
+++ b/config/dev.exs.sample
@@ -4,4 +4,5 @@ config :elixir_authorizenet,
   environment: :sandbox,
   validation_mode: :none, # :test, :live, or :none
   login_id: "login_id",
-  transaction_key: "transaction_key"
+  transaction_key: "transaction_key",
+  mix_env: :dev
diff --git a/config/test.exs b/config/test.exs
index 549639f..c43cd09 100644
--- a/config/test.exs
+++ b/config/test.exs
@@ -5,4 +5,5 @@ config :elixir_authorizenet,
   environment: :test,
   validation_mode: :none, # :test, :live, or :none
   login_id: "login_id",
-  transaction_key: "transaction_key"
+  transaction_key: "transaction_key",
+  mix_env: :test
diff --git a/lib/elixir_authorizenet.ex b/lib/elixir_authorizenet.ex
index fceacc3..7ea125b 100644
--- a/lib/elixir_authorizenet.ex
+++ b/lib/elixir_authorizenet.ex
@@ -84,7 +84,7 @@ defmodule AuthorizeNet do
   end
 
   defp uri() do
-    if Mix.env === :test do
+    if config(:mix_env) && config(:mix_env) === :test do
       config :test_server_uri
     else
       @uris[config(:environment)]