diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 4e6b2bb..bb126e3 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -21,9 +21,9 @@ jobs:
       - name: Configure Bundler
         run: |
           ruby -v
-          gem update --system
+          # gem update --system
           gem --version
-          gem install -N bundler
+          gem install -N bundler -v 2.4
 
       - uses: actions/cache@v3
         with:
diff --git a/lib/fcmpush/client.rb b/lib/fcmpush/client.rb
index b953288..b815b39 100644
--- a/lib/fcmpush/client.rb
+++ b/lib/fcmpush/client.rb
@@ -26,7 +26,11 @@ def initialize(domain, project_id, configuration, **options)
       @server_key = configuration.server_key
       @connection = Net::HTTP::Persistent.new
 
-      if configuration.proxy && configuration.proxy[:uri]
+      if !configuration.proxy
+        # do nothing
+      elsif configuration.proxy == :ENV
+        @connection.proxy = :ENV
+      elsif configuration.proxy && configuration.proxy[:uri]
         uri = URI(configuration.proxy[:uri])
         # user name must not be a empty string, password can
         if configuration.proxy[:user] && configuration.proxy[:user].strip != ''
@@ -34,8 +38,6 @@ def initialize(domain, project_id, configuration, **options)
           uri.password = configuration.proxy[:password] if configuration.proxy[:password]
         end
         @connection.proxy = uri
-      elsif configuration.proxy != false
-        @connection.proxy = :ENV
       end
     end