QByteArray::isNull() doesn't work properly under CMake

When using the default constructor for QByteArray, isNull() returns false when the project is compiled under CMake. Passing null to the QByteArray constructor works correctly. Both constructors properly return true for isNull() under QMake.

QByteArray().isNull() // True under qmake, false under cmake
QByteArray(NULL).isNull() // True under qmake and cmake

When running the attached sample program under gdb, the internal d pointer is different for the default constructor and for passing in NULL. My theory is that this has something to do with the inline default constructor, though I'm not sure why it would work under qmake but not under cmake.