Unexpected Ctrl+Enter behavior on reply

When I'm pressing Ctrl+Enter on reply (creating new topic, not quick reply) the input data is cleared, page is reloaded and nothing happens.

I've encountered with this on my local board, then I tried to install new board from scratch and was able to reproduce.

Analyzing Fiddler sessions I found one difference: broken request does not contain Post field inside:

-----------------------------243571392813808

Content-Disposition: form-data; name="post"

Submit

Btw, the issue is reproduced on phpBB forum, too.

Steps to reproduce:

Click on New Topic button;
Type any text;
Press Ctrl+Enter.

*Expected: *Nothing or sending the message;

*Actual: *page refreshes with loosing all input data.