diff --git a/CHANGELOG.md b/CHANGELOG.md
index 261ba8f2..90cef0ad 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -72,7 +72,6 @@
 * [#846](https://github.com/ruby-grape/grape-swagger/pull/846): Refactor oapi fetch task [@Vachman](https://github.com/Vachman)
 * [#850](https://github.com/ruby-grape/grape-swagger/pull/850): Fix value of enum to be Array [@takahashim](https://github.com/takahashim)
 
-
 ### 1.4.3 (January 5, 2022)
 
 #### Fixes
diff --git a/lib/grape-swagger.rb b/lib/grape-swagger.rb
index d2a7a78b..f2691846 100644
--- a/lib/grape-swagger.rb
+++ b/lib/grape-swagger.rb
@@ -40,7 +40,7 @@ def combine_routes(app, doc_klass)
       @target_class.combined_routes[resource] ||= []
       next if doc_klass.hide_documentation_path && route.path.match(/#{doc_klass.mount_path}($|\/|\(\.)/)
 
-      @target_class.combined_routes[resource].unshift route
+      @target_class.combined_routes[resource] << route
     end
   end
 
diff --git a/lib/grape-swagger/rake/oapi_tasks.rb b/lib/grape-swagger/rake/oapi_tasks.rb
index caaf63d4..20a35c76 100644
--- a/lib/grape-swagger/rake/oapi_tasks.rb
+++ b/lib/grape-swagger/rake/oapi_tasks.rb
@@ -63,7 +63,7 @@ def validate
           resource - if given only for that it would be generated (optional)'
         task validate: :environment do
           # :nocov:
-          ENV['store'] = 'true'
+          ENV.store('store', 'true')
           ::Rake::Task['oapi:fetch'].invoke
           exit if error?
 
@@ -108,7 +108,7 @@ def format_path(path)
       end
 
       def save_to_file?
-        ENV['store'].present? && !error?
+        ENV.fetch('store', nil).present? && !error?
       end
 
       def error?
@@ -118,10 +118,10 @@ def error?
       def file(url)
         api_version = url.split('/').last
 
-        name = if ENV['store'] == 'true' || ENV['store'].blank?
+        name = if ENV.fetch('store', nil) == 'true' || ENV.fetch('store', nil).blank?
                  "swagger_doc_#{api_version}.json"
                else
-                 ENV['store'].sub('.json', "_#{api_version}.json")
+                 ENV.fetch('store').sub('.json', "_#{api_version}.json")
                end
 
         File.join(Dir.getwd, name)
diff --git a/spec/swagger_v2/mount_override_api_spec.rb b/spec/swagger_v2/mount_override_api_spec.rb
index 1f2eb256..4d086de1 100644
--- a/spec/swagger_v2/mount_override_api_spec.rb
+++ b/spec/swagger_v2/mount_override_api_spec.rb
@@ -25,24 +25,13 @@ def app
     end
 
     Class.new(Grape::API) do
-      mount new_api
       mount old_api
+      mount new_api
 
       add_swagger_documentation format: :json
     end
   end
 
-  context 'actual api request' do
-    subject do
-      get '/'
-      last_response.body
-    end
-
-    it 'returns data from new endpoint' do
-      is_expected.to eq 'new'
-    end
-  end
-
   context 'api documentation' do
     subject do
       get '/swagger_doc'