mathgl doesn't pick up gsl

[annacegu@…]

I am compiling a C++ program that uses mathgl, and I am getting the following error: /opt/local/include/mgl2/datac_cf.h:30:8: error: definition of type 'gsl_matrix' conflicts with typedef of the same name struct gsl_matrix;

/opt/local/include/gsl/gsl_matrix_double.h:50:3: note: 'gsl_matrix' declared here } gsl_matrix;

Looking at data_cf.h, it seems like MGL_HAVE_GSL is switched off, so mathgl is not picking up GSL headers.