R# showing error message when using (!) (aka bang) in variable declaration for TypeScript

Hello, I have the following code written in TypeScript, and I get the following error message:

The bang (!) is something available in TypeScript 2.7.  (I just learned about it today)

https://blogs.msdn.microsoft.com/typescript/2018/01/31/announcing-typescript-2-7/ 

It offers "deferred-initialization".

I'm guessing R# maybe doesn't recognize the syntax?  It compiles and runs fine.  Is there anyway to disable the error message?

Thanks,

Eric