diff --git a/appium/webdriver/appium_service.py b/appium/webdriver/appium_service.py
index 33932265..a3d7b0dc 100644
--- a/appium/webdriver/appium_service.py
+++ b/appium/webdriver/appium_service.py
@@ -127,7 +127,7 @@ def start(self, **kwargs: Any) -> sp.Popen:
             raise AppiumServiceError(error_msg)
         return self._process
 
-    def stop(self, timeout=5.5) -> bool:
+    def stop(self, timeout: float = 5.5) -> bool:
         """Stops Appium service if it is running.
 
         The call will be ignored if the service is not running