Instruction's getExpandedArguments() does not quoted variables correctly

[rcjsuen]

import { DockerfileParser } from './main'
let dockerfile = DockerfileParser.parse("FROM scratch\nENV VAR=value\nRUN echo \"$VAR\"");
let args = dockerfile.getInstructions()[2].getExpandedArguments();
console.log(args[1].getValue());

"value

It seems like the closing quotation mark is being dropped.