diff --git a/.gitignore b/.gitignore
index 1a27888..d3f49c0 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,5 +1,6 @@
 *.gem
 .bundle
+.idea
 Gemfile.lock
 pkg/*
 coverage
diff --git a/lib/omniauth-square/version.rb b/lib/omniauth-square/version.rb
index f28edae..340a66f 100644
--- a/lib/omniauth-square/version.rb
+++ b/lib/omniauth-square/version.rb
@@ -1,5 +1,5 @@
 module Omniauth
   module Square
-    VERSION = "1.0.2"
+    VERSION = "1.0.3"
   end
 end
diff --git a/lib/omniauth/strategies/square.rb b/lib/omniauth/strategies/square.rb
index 924e05e..4539cf2 100644
--- a/lib/omniauth/strategies/square.rb
+++ b/lib/omniauth/strategies/square.rb
@@ -30,13 +30,24 @@ def raw_info
         @raw_info ||= access_token.get('/v1/me').parsed
       end
 
+      alias :old_request_phase :request_phase
+
+      def request_phase
+        if request.params['plan_id']
+          options[:authorize_params][:plan_id] = request.params['plan_id']
+        end
+
+        old_request_phase
+      end
+
       protected
 
       def build_access_token
         parsed_response = fetch_access_token
 
         parsed_response['expires_at'] = Time.parse(parsed_response['expires_at']).to_i
-        parsed_response.merge!(deep_symbolize(options.auth_token_params))
+        auth_token_params = options.auth_token_params || {}
+        parsed_response.merge!(deep_symbolize(auth_token_params))
 
         connect_client = client.dup
         connect_client.site = options.client_options.connect_site
diff --git a/omniauth-square.gemspec b/omniauth-square.gemspec
index a8f18fb..03fd374 100644
--- a/omniauth-square.gemspec
+++ b/omniauth-square.gemspec
@@ -24,4 +24,5 @@ Gem::Specification.new do |s|
   s.add_development_dependency 'rack-test'
   s.add_development_dependency 'simplecov'
   s.add_development_dependency 'webmock'
+  s.add_development_dependency 'pry'
 end
diff --git a/spec/omniauth/strategies/square_spec.rb b/spec/omniauth/strategies/square_spec.rb
index 330a446..91a2c3f 100644
--- a/spec/omniauth/strategies/square_spec.rb
+++ b/spec/omniauth/strategies/square_spec.rb
@@ -2,7 +2,7 @@
 
 describe OmniAuth::Strategies::Square do
   before :each do
-    @request = double('Request', :scheme => '', :url => '')
+    @request = double('Request', :scheme => '', :url => '', :params => {}, :cookies => {}, :env => {})
     @request.stub(:params) { {} }
   end
 
@@ -150,6 +150,18 @@
     end
   end
 
+  describe '#request_phase' do
+    before do
+      @request.stub(:params).and_return('plan_id' => 'test_plan_id')
+      subject.stub(:old_request_phase).and_return(:something)
+    end
+
+    it 'adds `plan_id` parameter to `authorize_params`' do
+      expect { subject.request_phase }.to change { subject.options.authorize_params.plan_id }.
+        from(nil).to('test_plan_id')
+    end
+  end
+
   describe '#access_token_request_payload' do
     before do
       @request.stub(:params).and_return('code' => '11111')
diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
index c18d39e..4a70d94 100644
--- a/spec/spec_helper.rb
+++ b/spec/spec_helper.rb
@@ -5,6 +5,7 @@
 require 'webmock/rspec'
 require 'omniauth'
 require 'omniauth-square'
+require 'pry'
 
 RSpec.configure do |config|
   config.include WebMock::API