diff --git a/lib/oauth2/client.ex b/lib/oauth2/client.ex
index 59beb12..8f20427 100644
--- a/lib/oauth2/client.ex
+++ b/lib/oauth2/client.ex
@@ -223,7 +223,7 @@ defmodule OAuth2.Client do
   @spec put_serializer(t, binary, atom) :: t
   def put_serializer(%Client{serializers: serializers} = client, mime, module)
       when is_binary(mime) and is_atom(module) do
-    %Client{client | serializers: Map.put(serializers, mime, module)}
+    %{client | serializers: Map.put(serializers, mime, module)}
   end
 
   @doc """
@@ -238,7 +238,7 @@ defmodule OAuth2.Client do
   """
   @spec delete_serializer(t, binary) :: t
   def delete_serializer(%Client{serializers: serializers} = client, mime) do
-    %Client{client | serializers: Map.delete(serializers, mime)}
+    %{client | serializers: Map.delete(serializers, mime)}
   end
 
   @doc false
diff --git a/mix.exs b/mix.exs
index 5667ad5..c01dff9 100644
--- a/mix.exs
+++ b/mix.exs
@@ -5,6 +5,20 @@ defmodule OAuth2.Mixfile do
   @version "2.1.0"
 
   def project do
+    maybe_cli =
+      if Version.compare(System.version(), "1.14.5") == :gt do
+        []
+      else
+        [
+          preferred_cli_env: [
+            coveralls: :test,
+            "coveralls.detail": :test,
+            "coveralls.html": :test,
+            docs: :dev
+          ]
+        ]
+      end
+
     [
       app: :oauth2,
       name: "OAuth2",
@@ -16,14 +30,8 @@ defmodule OAuth2.Mixfile do
       docs: docs(),
       elixirc_paths: elixirc_paths(Mix.env()),
       test_coverage: [tool: ExCoveralls],
-      preferred_cli_env: [
-        coveralls: :test,
-        "coveralls.detail": :test,
-        "coveralls.html": :test,
-        docs: :dev
-      ],
       dialyzer: dialyzer()
-    ]
+    ] ++ maybe_cli
   end
 
   def application do
@@ -81,6 +89,19 @@ defmodule OAuth2.Mixfile do
     ]
   end
 
+  if Version.compare(System.version(), "1.14.5") == :gt do
+    def cli do
+      [
+        preferred_envs: [
+          coveralls: :test,
+          "coveralls.detail": :test,
+          "coveralls.html": :test,
+          docs: :dev
+        ]
+      ]
+    end
+  end
+
   defp elixirc_paths(:test), do: ["lib", "test/support"]
   defp elixirc_paths(_), do: ["lib"]
 end