Typescript error on building: error TS9005: Declaration emit for this file requires using private name

[mliebelt]

When doing a build (clean; buildpeg; build) on the current version (with updated Typescript dependencies), I get an error when compiling.

> tsc -p tsconfig-mjs.json
src/_pgn-parser.js:4:1 - error TS9005: Declaration emit for this file requires using private name 'peg$SyntaxError'. An explicit type annotation may unblock declaration emit.

4 (function(root, factory) {
  ~
Found 1 error in src/_pgn-parser.js:4
Process finished with exit code 1

The build then stops, so the following steps npm run umd && npm run dts are not done. So I have to find out how to do an "explicit type annotation for peg$SyntaxError.