Build error for "unused" lightcone function

I am getting this error when building SWIFT with both GCC and ICC:

lightcone/projected_kernel.c(47): error #177: function "projected_kernel_integrand" was declared but never referenced
  static double projected_kernel_integrand(double qz, void *param) {
                ^

The problem arises because the function is passed as a function pointer to GSL:

gsl_function F = {&projected_kernel_integrand, &qxy};

Removing static fixes this issue.