MathML generation error involving sin^2

[NSoiffer]

Description

$text('mathML') returns incorrect MathML for \sin ^2\left(x\right). It returns
<mrow><msup><mo>sin</mo><mn>2</mn></msup><mrow><mo>(</mo><mi>x</mi><mo>)</mo></mrow></mrow>

Steps to Reproduce

I have attached a file that reproduces the problem:
sinbug.zip

Unzip this to get an HTML file (can't attach HTML files directly) and that will show the error. This is a clone of examples/basic/index.html and the file references are relative to that location.

[arnog]

What mathML do you expect? This appears to be valid mathML and it displays correctly in Safari.

[NSoiffer]

That is indeed the correct MathML, but if you type sin^2 (x) ('space' to get out of exponent), you see different MathML:
<mrow><mo extid="phcusk">sin</mo><mo> &ApplyFunction; </mo><mrow><mo extid="phcuso">(</mo><mi extid="phcusm">x</mi><mo extid="phcuso">)</mo></mrow></mrow>
(apologies, I apparently pasted the correct in the initial bug report). Notice that there is no msup.

If you have trouble reproducing it, open the attached file in the initial bug report -- perhaps one of the config settings is causing the bug.

[arnog]

OK, got it. This happens only when typing the formula, not if pasting it.