Problem with widget stylesheets in 4.5.3 on Linux

[Lendrick]

Greets!

I'm having a bit of issue trying to create a label with a transparent background using a stylesheet. Everything seems to work, except I get a weird radial gradient that I didn't ask for...

testLabel = new QLabel("Hello, world!");
  testLabel->setStyleSheet(
    "background-color: rgba(255, 255, 255, 0%);"
    "font-size: 20px;"
  );
  addWidget(testLabel);

testLabel = new QLabel("Hello, world!");
  testLabel->setStyleSheet(
    "background-color: rgba(255, 255, 255, 0%);"
    "font-size: 20px;"
  );
  addWidget(testLabel);

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I've attached an image that shows what I'm talking about.

Any idea where that gradient is coming from and how I can get rid of it? It appears to happen on buttons too.