Has parent/child resizeEvent calling order changed since Qt5.1.1?

[Kirinyale]

I came back to my Qt project after a break and upgraded it from 5.1.1 to 5.5. Now I've found at least one feature that is broken for a reason I don't quite understand...

I have a dialog with an expanding QLabel. Layout is built in such a way that this label covers most of the dialog width with any reasonable size. I'm attaching a screenshot from Designer for clarity - the QLabel in question (tilesImage_) is selected.

For some reason, when QDialog::resizeEvent() gets called after creating the dialog, tilesImage_ still has wrong size (much smaller than it should be, e.g. 100x64 when the dialog is 688x411). My code relied on the fact that all widget sizes are properly updated at this point, and this definitely worked in Qt 5.1.1 (I just checked an old build). Apparently, something important changed between 5.1.1 and 5.5 in this regard. Is there any documentation about this change? Any workarounds (except installing an event filter to each separate widget I need to check)?