diff --git a/lib/ex_oauth2_provider/access_grants/access_grant.ex b/lib/ex_oauth2_provider/access_grants/access_grant.ex
index 6f26d59c..e0533491 100644
--- a/lib/ex_oauth2_provider/access_grants/access_grant.ex
+++ b/lib/ex_oauth2_provider/access_grants/access_grant.ex
@@ -46,11 +46,33 @@ defmodule ExOauth2Provider.AccessGrants.AccessGrant do
     ]
   end
 
+  @doc false
+  def access_grant_allowed_fields do
+    [:redirect_uri, :expires_in, :scopes]
+  end
+
+  @doc false
+  def access_grant_required_fields do
+    [:redirect_uri, :expires_in, :token, :resource_owner, :application]
+  end
+
+  @doc false
+  def access_grant_request_fields do
+    ["redirect_uri", "scope"]
+  end
+
   defmacro __using__(config) do
     quote do
+      use ExOauth2Provider.Changeset
       use ExOauth2Provider.Schema, unquote(config)
 
-      import unquote(__MODULE__), only: [access_grant_fields: 0]
+      import unquote(__MODULE__),
+        only: [
+          access_grant_fields: 0,
+          access_grant_allowed_fields: 0,
+          access_grant_required_fields: 0,
+          access_grant_request_fields: 0
+        ]
     end
   end
 
@@ -61,18 +83,18 @@ defmodule ExOauth2Provider.AccessGrants.AccessGrant do
   end
 
   alias Ecto.Changeset
-  alias ExOauth2Provider.{Mixin.Scopes, Utils}
+  alias ExOauth2Provider.{Config, Mixin.Scopes, Utils}
 
   @spec changeset(Ecto.Schema.t(), map(), keyword()) :: Changeset.t()
   def changeset(grant, params, config) do
     grant
-    |> Changeset.cast(params, [:redirect_uri, :expires_in, :scopes])
+    |> Changeset.cast(params, Config.access_grant(config).allowed_fields())
     |> Changeset.assoc_constraint(:application)
     |> Changeset.assoc_constraint(:resource_owner)
     |> put_token()
     |> Scopes.put_scopes(grant.application.scopes, config)
     |> Scopes.validate_scopes(grant.application.scopes, config)
-    |> Changeset.validate_required([:redirect_uri, :expires_in, :token, :resource_owner, :application])
+    |> Changeset.validate_required(Config.access_grant(config).required_fields())
     |> Changeset.unique_constraint(:token)
   end
 
diff --git a/lib/ex_oauth2_provider/access_tokens/access_token.ex b/lib/ex_oauth2_provider/access_tokens/access_token.ex
index 49242a3e..164fc316 100644
--- a/lib/ex_oauth2_provider/access_tokens/access_token.ex
+++ b/lib/ex_oauth2_provider/access_tokens/access_token.ex
@@ -49,11 +49,33 @@ defmodule ExOauth2Provider.AccessTokens.AccessToken do
     ]
   end
 
+  @doc false
+  def access_token_allowed_fields do
+    [:expires_in, :scopes]
+  end
+
+  @doc false
+  def access_token_required_fields do
+    [:expires_in]
+  end
+
+  @doc false
+  def access_token_request_fields do
+    []
+  end
+
   defmacro __using__(config) do
     quote do
+      use ExOauth2Provider.Changeset
       use ExOauth2Provider.Schema, unquote(config)
 
-      import unquote(__MODULE__), only: [access_token_fields: 0]
+      import unquote(__MODULE__),
+        only: [
+          access_token_fields: 0,
+          access_token_allowed_fields: 0,
+          access_token_required_fields: 0,
+          access_token_request_fields: 0
+        ]
     end
   end
 
@@ -71,13 +93,14 @@ defmodule ExOauth2Provider.AccessTokens.AccessToken do
     server_scopes = server_scopes(token)
 
     token
-    |> Changeset.cast(params, [:expires_in, :scopes])
+    |> Changeset.cast(params, Config.access_token(config).allowed_fields())
     |> validate_application_or_resource_owner()
     |> put_previous_refresh_token(params[:previous_refresh_token])
     |> put_refresh_token(params[:use_refresh_token])
     |> Scopes.put_scopes(server_scopes, config)
     |> Scopes.validate_scopes(server_scopes, config)
     |> put_token(config)
+    |> Changeset.validate_required(Config.access_token(config).required_fields())
   end
 
   defp server_scopes(%{application: %{scopes: scopes}}), do: scopes
diff --git a/lib/ex_oauth2_provider/changeset.ex b/lib/ex_oauth2_provider/changeset.ex
new file mode 100644
index 00000000..c5235116
--- /dev/null
+++ b/lib/ex_oauth2_provider/changeset.ex
@@ -0,0 +1,14 @@
+defmodule ExOauth2Provider.Changeset do
+  @moduledoc """
+  This module defines behaviour for oauth changesets
+  """
+  @callback allowed_fields() :: nonempty_list(atom())
+  @callback required_fields() :: nonempty_list(atom())
+  @callback request_fields() :: nonempty_list(binary())
+
+  defmacro __using__(_) do
+    quote do
+      @behaviour ExOauth2Provider.Changeset
+    end
+  end
+end
diff --git a/lib/ex_oauth2_provider/oauth2/authorization/strategy/code.ex b/lib/ex_oauth2_provider/oauth2/authorization/strategy/code.ex
index 40b3cb02..5eb94c13 100644
--- a/lib/ex_oauth2_provider/oauth2/authorization/strategy/code.ex
+++ b/lib/ex_oauth2_provider/oauth2/authorization/strategy/code.ex
@@ -104,7 +104,13 @@ defmodule ExOauth2Provider.Authorization.Code do
   end
 
   defp reissue_grant({:error, params}, _config), do: {:error, params}
-  defp reissue_grant({:ok, %{access_token: _access_token} = params}, config), do: issue_grant({:ok, params}, config)
+  defp reissue_grant({:ok, %{access_token: access_token} = params}, config) do
+    params =
+      access_token
+      |> Map.take(Config.access_token(config).allowed_fields())
+      |> Map.merge(params)
+    issue_grant({:ok, params}, config)
+  end
   defp reissue_grant({:ok, params}, _config), do: {:ok, params}
 
   @doc """
@@ -142,18 +148,21 @@ defmodule ExOauth2Provider.Authorization.Code do
   defp issue_grant({:ok, %{resource_owner: resource_owner, client: application, request: request} = params}, config) do
     grant_params =
       request
-      |> Map.take(["redirect_uri", "scope"])
+      |> Map.take(Config.access_grant(config).request_fields())
+      |> Map.merge(Map.take(params, Config.access_grant(config).allowed_fields()))
       |> Map.new(fn {k, v} ->
         case k do
           "scope" -> {:scopes, v}
-          _       -> {String.to_atom(k), v}
+          "" <> _ -> {String.to_atom(k), v}
+          _       -> {k, v}
         end
       end)
       |> Map.put(:expires_in, Config.authorization_code_expires_in(config))
 
     case AccessGrants.create_grant(resource_owner, application, grant_params, config) do
       {:ok, grant}    -> {:ok, Map.put(params, :grant, grant)}
-      {:error, error} -> Error.add_error({:ok, params}, error)
+      {:error, {:error, _, _} = error} -> Error.add_error({:ok, params}, error)
+      {:error, _} -> Error.add_error({:ok, params}, Error.server_error())
     end
   end
 
diff --git a/lib/ex_oauth2_provider/oauth2/token/strategy/authorization_code.ex b/lib/ex_oauth2_provider/oauth2/token/strategy/authorization_code.ex
index d1c1abe7..375923db 100644
--- a/lib/ex_oauth2_provider/oauth2/token/strategy/authorization_code.ex
+++ b/lib/ex_oauth2_provider/oauth2/token/strategy/authorization_code.ex
@@ -37,14 +37,23 @@ defmodule ExOauth2Provider.Token.AuthorizationCode do
   end
 
   defp issue_access_token_by_grant({:error, params}, _config), do: {:error, params}
-  defp issue_access_token_by_grant({:ok, %{access_grant: access_grant, request: _} = params}, config) do
-    token_params = %{use_refresh_token: Config.use_refresh_token?(config)}
 
-    result = Config.repo(config).transaction(fn ->
-      access_grant
-      |> revoke_grant(config)
-      |> maybe_create_access_token(token_params, config)
-    end)
+  defp issue_access_token_by_grant(
+         {:ok, %{access_grant: access_grant, request: request} = params},
+         config
+       ) do
+    token_params =
+      request
+      |> Map.take(Config.access_token(config).request_fields())
+      |> Map.new(fn {k, v} -> {String.to_atom(k), v} end)
+      |> Map.put(:use_refresh_token, Config.use_refresh_token?(config))
+
+    result =
+      Config.repo(config).transaction(fn ->
+        access_grant
+        |> revoke_grant(config)
+        |> maybe_create_access_token(token_params, config)
+      end)
 
     case result do
       {:ok, {:error, error}}     -> Error.add_error({:ok, params}, error)
@@ -57,8 +66,19 @@ defmodule ExOauth2Provider.Token.AuthorizationCode do
     do: AccessGrants.revoke(access_grant, config)
 
   defp maybe_create_access_token({:error, _} = error, _token_params, _config), do: error
-  defp maybe_create_access_token({:ok, %{resource_owner: resource_owner, application: application, scopes: scopes}}, token_params, config) do
-    token_params = Map.merge(token_params, %{scopes: scopes, application: application})
+
+  defp maybe_create_access_token(
+         {:ok,
+          %{resource_owner: resource_owner, application: application, scopes: scopes} = grant},
+         token_params,
+         config
+       ) do
+    token_params =
+      grant
+      |> Map.drop([:expires_in, :scopes])
+      |> Map.take(Config.access_token(config).allowed_fields())
+      |> Map.merge(token_params)
+      |> Map.merge(%{scopes: scopes, application: application})
 
     resource_owner
     |> AccessTokens.get_token_for(application, scopes, config)
diff --git a/lib/ex_oauth2_provider/oauth2/token/strategy/refresh_token.ex b/lib/ex_oauth2_provider/oauth2/token/strategy/refresh_token.ex
index dc4df7cf..2050d228 100644
--- a/lib/ex_oauth2_provider/oauth2/token/strategy/refresh_token.ex
+++ b/lib/ex_oauth2_provider/oauth2/token/strategy/refresh_token.ex
@@ -49,17 +49,29 @@ defmodule ExOauth2Provider.Token.RefreshToken do
   defp load_access_token_by_refresh_token(params, _config), do: Error.add_error(params, Error.invalid_request())
 
   defp issue_access_token_by_refresh_token({:error, params}, _config), do: {:error, params}
-  defp issue_access_token_by_refresh_token({:ok, %{refresh_token: refresh_token, request: _} = params}, config) do
-    result = Config.repo(config).transaction(fn ->
-      token_params = token_params(refresh_token, config)
 
-      refresh_token
-      |> revoke_access_token(config)
-      |> case do
-        {:ok, %{resource_owner: resource_owner}} -> AccessTokens.create_token(resource_owner, token_params, config)
-        {:error, error}     -> {:error, error}
-      end
-    end)
+  defp issue_access_token_by_refresh_token(
+         {:ok, %{refresh_token: refresh_token, request: request} = params},
+         config
+       ) do
+    result =
+      Config.repo(config).transaction(fn ->
+        token_params =
+          request
+          |> Map.take(Config.access_token(config).request_fields())
+          |> Map.new(fn {k, v} -> {String.to_atom(k), v} end)
+          |> Map.merge(token_params(refresh_token, config))
+
+        refresh_token
+        |> revoke_access_token(config)
+        |> case do
+          {:ok, %{resource_owner: resource_owner}} ->
+            AccessTokens.create_token(resource_owner, token_params, config)
+
+          {:error, error} ->
+            {:error, error}
+        end
+      end)
 
     case result do
       {:ok, {:error, error}}     -> Error.add_error({:ok, params}, error)
@@ -69,7 +81,11 @@ defmodule ExOauth2Provider.Token.RefreshToken do
   end
 
   defp token_params(%{scopes: scopes, application: application} = refresh_token, config) do
-    params = %{scopes: scopes, application: application, use_refresh_token: true}
+    params =
+      refresh_token
+      |> Map.drop([:expires_in, :scopes])
+      |> Map.take(Config.access_token(config).allowed_fields())
+      |> Map.merge(%{scopes: scopes, application: application, use_refresh_token: true})
 
     case Config.refresh_token_revoked_on_use?(config) do
       true  -> Map.put(params, :previous_refresh_token, refresh_token)
diff --git a/lib/mix/ex_oauth2_provider/schema.ex b/lib/mix/ex_oauth2_provider/schema.ex
index ceced4d6..7d3f1167 100644
--- a/lib/mix/ex_oauth2_provider/schema.ex
+++ b/lib/mix/ex_oauth2_provider/schema.ex
@@ -11,21 +11,40 @@ defmodule Mix.ExOauth2Provider.Schema do
   <%= if schema.binary_id do %>
     @primary_key {:id, :binary_id, autogenerate: true}
     @foreign_key_type :binary_id<% end %>
-    schema <%= inspect schema.table %> do
-      <%= schema.macro_fields %>()
+    schema <%= inspect schema.table_name %> do
+      <%= schema.table %>_fields()
 
       timestamps()
+    end<%= if schema.changeset do %>
+
+    @impl ExOauth2Provider.Changeset
+    def allowed_fields do
+      <%= schema.table %>_allowed_fields()
+    end
+
+    @impl ExOauth2Provider.Changeset
+    def required_fields do
+      <%= schema.table %>_required_fields()
     end
+
+    @impl ExOauth2Provider.Changeset
+    def request_fields do
+      <%= schema.table %>_request_fields()
+    end<% end %>
   end
   """
 
   alias ExOauth2Provider.{AccessGrants.AccessGrant, AccessTokens.AccessToken, Applications.Application}
 
-  @schemas [{"application", Application}, {"access_grant", AccessGrant}, {"access_token", AccessToken}]
+  @schemas [
+    {"application", Application, false},
+    {"access_grant", AccessGrant, true},
+    {"access_token", AccessToken, true}
+  ]
 
   @spec create_schema_files(atom(), binary(), keyword()) :: any()
   def create_schema_files(context_app, namespace, opts) do
-    for {table, schema} <- @schemas do
+    for {table, schema, changeset} <- @schemas do
       app_base     = Config.app_base(context_app)
       table_name   = "#{namespace}_#{table}s"
       context      = Macro.camelize(table_name)
@@ -34,8 +53,7 @@ defmodule Mix.ExOauth2Provider.Schema do
       module       = Module.concat([app_base, context, module])
       binary_id    = Keyword.get(opts, :binary_id, false)
       macro        = schema
-      macro_fields = "#{table}_fields"
-      content      = EEx.eval_string(@template, schema: %{module: module, table: table_name, binary_id: binary_id, macro: macro, macro_fields: macro_fields}, otp_app: context_app)
+      content      = EEx.eval_string(@template, schema: %{module: module, table: table, table_name: table_name, binary_id: binary_id, macro: macro, changeset: changeset}, otp_app: context_app)
       dir          = "lib/#{context_app}/#{Macro.underscore(context)}/"
 
       File.mkdir_p!(dir)
diff --git a/test/support/lib/dummy/oauth_access_grants/oauth_access_grant.ex b/test/support/lib/dummy/oauth_access_grants/oauth_access_grant.ex
index 8b330c15..35d0e05b 100644
--- a/test/support/lib/dummy/oauth_access_grants/oauth_access_grant.ex
+++ b/test/support/lib/dummy/oauth_access_grants/oauth_access_grant.ex
@@ -13,4 +13,19 @@ defmodule Dummy.OauthAccessGrants.OauthAccessGrant do
     access_grant_fields()
     timestamps()
   end
+
+  @impl ExOauth2Provider.Changeset
+  def allowed_fields do
+    access_grant_allowed_fields()
+  end
+
+  @impl ExOauth2Provider.Changeset
+  def required_fields do
+    access_grant_required_fields()
+  end
+
+  @impl ExOauth2Provider.Changeset
+  def request_fields do
+    access_grant_request_fields()
+  end
 end
diff --git a/test/support/lib/dummy/oauth_access_tokens/oauth_access_token.ex b/test/support/lib/dummy/oauth_access_tokens/oauth_access_token.ex
index f2e59941..c9ec8e32 100644
--- a/test/support/lib/dummy/oauth_access_tokens/oauth_access_token.ex
+++ b/test/support/lib/dummy/oauth_access_tokens/oauth_access_token.ex
@@ -13,4 +13,19 @@ defmodule Dummy.OauthAccessTokens.OauthAccessToken do
     access_token_fields()
     timestamps()
   end
+
+  @impl ExOauth2Provider.Changeset
+  def allowed_fields do
+    access_token_allowed_fields()
+  end
+
+  @impl ExOauth2Provider.Changeset
+  def required_fields do
+    access_token_required_fields()
+  end
+
+  @impl ExOauth2Provider.Changeset
+  def request_fields do
+    access_token_request_fields()
+  end
 end