appium: getSize not working in Linux appium 1.9.1

The problem

I have hybrid app and Im trying the below method MobileDriver.FindElement(LocateElement(type, object)).Size which works fine when running in windows machine with appium server 1.9.1 here is the windows gist When I try to run the same code in Linux machine with appium server 1.9.1 it fails with error “Unknown command”. Here is the gist for linux appium server linux gist

Environment

• Appium version (or git revision) that exhibits the issue: 1.9.1
• Last Appium version that did not exhibit the issue (if applicable): 1.8.1
• Desktop OS/version used to run Appium: Linux and Windows 10
• Node.js version (unless using Appium.app|exe):
• Mobile platform/version under test: Android o
• Real device or emulator/simulator: real
• Appium CLI or Appium.app|exe: CLI for linux and Exe for windows

Details

<add key="AppiumServer" value="127.0.0.1" /> <add key="AppiumServerPort" value="4723" /> <add key="PlatformName" value="Android" /> <add key="AutomationName" value="uia" /> <add key="PlatformVersion" value="8.0" /> <add key="DeviceName" value="xxxxxxx" /> <add key="AppPackage" value="com.xxx.xxx" /> <add key="AppActivity" value=".MainActivity" /> <add key="AutoWebview" value="true" />