Calling QFileDialog::getExistingDirectory with default parameters:

QString Path = "C:\";
QFileDialog::getExistingDirectory( this, "Choose Directory", Path );

Generates a warning in QWindowsNativeFileDialogBase::selectNameFilter:

"QWindowsNativeFileDialogBase::selectNameFilter: Invalid parameter 'Directories' not found in 'All Files '."

When the QWindowsNativeFileDialogBase is being created it gets a default name filter of "All Files " even though QFileDialogOptionsPrivate::initiallySelectedNameFilter is set to "Directories".

Unfortunately there is no work around as you can't pass a filter in to getExistingDirectory to override the incorrect initial value.

There was a similar bug reported https://bugreports.qt-project.org/browse/QTBUG-30001 which was closed and reported as fixed but this is still an issue in later versions of Qt with that fix applied.