diff --git a/rb/lib/selenium/webdriver/firefox/service.rb b/rb/lib/selenium/webdriver/firefox/service.rb
index ce1526d1ef718..45fc17a38547d 100644
--- a/rb/lib/selenium/webdriver/firefox/service.rb
+++ b/rb/lib/selenium/webdriver/firefox/service.rb
@@ -25,6 +25,15 @@ class Service < WebDriver::Service
         EXECUTABLE = 'geckodriver'
         SHUTDOWN_SUPPORTED = false
         DRIVER_PATH_ENV_KEY = 'SE_GECKODRIVER'
+
+        def initialize(path: nil, port: nil, log: nil, args: nil)
+          args ||= []
+          unless args.any? { |arg| arg.include?('--connect-existing') }
+            args << '--websocket-port'
+            args << WebDriver::PortProber.above(9222).to_s
+          end
+          super
+        end
       end # Service
     end # Firefox
   end # WebDriver
diff --git a/rb/spec/integration/selenium/webdriver/firefox/service_spec.rb b/rb/spec/integration/selenium/webdriver/firefox/service_spec.rb
index 8cd66cc67619c..f9e3bf1cb105b 100644
--- a/rb/spec/integration/selenium/webdriver/firefox/service_spec.rb
+++ b/rb/spec/integration/selenium/webdriver/firefox/service_spec.rb
@@ -37,6 +37,21 @@ module Firefox
         it 'can be started outside driver' do
           expect(service_manager.uri).to be_a(URI)
         end
+
+        context 'with BiDi enabled', exclusive: {bidi: true, reason: 'only executed when bidi is enabled'} do
+          it 'ensures two service instances use different websocket port' do
+            service1 = described_class.new
+            service2 = described_class.new
+
+            ws_index1 = service1.args.index('--websocket-port')
+            ws_index2 = service2.args.index('--websocket-port')
+
+            port1 = service1.args[ws_index1 + 1].to_i
+            port2 = service2.args[ws_index2 + 1].to_i
+
+            expect(port1).not_to eq(port2)
+          end
+        end
       end
     end # Firefox
   end # WebDriver
diff --git a/rb/spec/unit/selenium/webdriver/firefox/service_spec.rb b/rb/spec/unit/selenium/webdriver/firefox/service_spec.rb
index 811894e74f4e3..674e8b654192d 100644
--- a/rb/spec/unit/selenium/webdriver/firefox/service_spec.rb
+++ b/rb/spec/unit/selenium/webdriver/firefox/service_spec.rb
@@ -51,7 +51,7 @@ module Firefox
           it 'does not create args by default' do
             service = described_class.new
 
-            expect(service.extra_args).to be_empty
+            expect(service.extra_args.count).to eq 2
           end
 
           it 'uses sets log path to stdout' do
@@ -73,9 +73,23 @@ module Firefox
           end
 
           it 'uses provided args' do
-            service = described_class.new(args: ['--foo', '--bar'])
+            service = described_class.new(args: %w[--foo --bar])
+            expect(service.extra_args).to include(*%w[--foo --bar])
+          end
 
-            expect(service.extra_args).to eq ['--foo', '--bar']
+          it 'there is a random port for websocket' do
+            service = described_class.new
+            ws_index = service.extra_args.index('--websocket-port')
+            port = service.extra_args[ws_index + 1].to_i
+            expect(port).to be_positive
+          end
+
+          context 'with connect existing' do
+            it 'does not uses websocket-port' do
+              service = described_class.new(args: ['--connect-existing'])
+              expect(service.extra_args).not_to include('--websocket-port')
+              expect(service.extra_args).to eq(['--connect-existing'])
+            end
           end
         end