TypeScript definition for ValueType not found

[JohannesMej]

When generating JavaScript/TypeScript for a very simple C# struct:

[JSExport] public struct Interface { ...

In the .d.ts file following is generated:

import './System.Collections';
import './System.Runtime';

export class Interface extends ValueType {...

ValueType is unknown to the typescript compiler:

Where is the TypeScript definition for ValueType or how can I avoid the TypeScript compiler error? Obviously there is no issue during runtime.

Is this an issue or do I overlook something?