Shared Memory Example won't work

Shared Memory Example won't work with showing "Unable to attach to shared memory segment. Load an image first".

https://doc.qt.io/qt-5/qtcore-ipc-sharedmemory-example.html

Reproducible steps:

1. Open example "Shared Memory Example" on Qt Creator
2. Build and run
3. Load image from file
4. Click "Display Image From Shared Memory"
5. Showing "Unable to attach to shared memory segment. Load an image first"

Always failing here.

void Dialog::loadFromMemory()
{
    if (!sharedMemory.attach()) {
        ui.label->setText(tr("Unable to attach to shared memory segment.\n" \
                             "Load an image first."));
        return;