Does not compile with OpenMP

When I pass -Dopenmp=true to cmake the output says

-- The following features have been enabled:

 * ScalaPACK, Scalapack linear algebra library https://www.netlib.org/scalapack/
 * Openmp, OpenMP API https://www.openmp.org/
 * real64, Build with double precision
 * shared, Build shared libraries

But when I use the solver it tells me

Entering DMUMPS 5.7.3 from C interface with JOB, N, NNZ =   6           2              4
      executing #MPI =      1, without OMP

How can I get it to use OMP?

scivision / mumps

Does not compile with OpenMP #102