The event binding code is using two if statements to check if an event is a key event or a mouse event.

if ( rkeyEvent.test( name ) ) {
  jQuery.event.fixHooks[ name ] = jQuery.event.keyHooks;
}

if ( rmouseEvent.test( name ) ) {
  jQuery.event.fixHooks[ name ] = jQuery.event.mouseHooks;
}

But based on the rkeyevent and rmouseevent regexs and the list of events it is impossible for an event to be both a mouse event and key event.

Therefore I rewrote it as an if/else if statement. I'm putting the mouseevent test first because it's more common. Pull request incoming.