Encryption in Firefox tampermonkey crashes

[Muph0]

When encrypting string with generated/imported keys, this userscript run in Firefox tampermonkey crashes with error

Error: Error encrypting message: Could not
find valid key packet for signing in key d713ea674b8e4752

suggesting that the key is expired, even if the key is newly generated.

However, the same code run in client code works alright. (see this jsfiddle)
I have also tested it in Chrome tampermonkey and the script runs ok. Probably a bug?

[twiss]

window.Symbol doesn't seem to be available in tampermonkey userscripts. If you set window.Symbol = unsafeWindow.Symbol before you load openpgp.js, it works.