Undefined symbols when including <pybind11.h>?

[hsetlik]

I have a C++ Qt application where pybind11 is included as a submodule. Setting up a python module from a PYBIND11_MODULE in the C++ source works as expected, but trying to compile the C++ project with <pybind11.h> included gives a linker error that begins: "Undefined symbols for architecture x86_64:" followed by a list of what seems to be every symbol beginning with "_Py". Any suggestions/ideas of why this happens are much appreciated!