diff --git a/var/spack/repos/builtin/packages/py-h5py/package.py b/var/spack/repos/builtin/packages/py-h5py/package.py
index 21105c08c4..39b352e4ae 100644
--- a/var/spack/repos/builtin/packages/py-h5py/package.py
+++ b/var/spack/repos/builtin/packages/py-h5py/package.py
@@ -54,10 +54,10 @@ class PyH5py(PythonPackage):
     phases = ['configure', 'install']
 
     def setup_build_environment(self, env):
+        env.set('HDF5_DIR', self.spec['hdf5'].prefix)
         if '+mpi' in self.spec:
             env.set('CC', self.spec['mpi'].mpicc)
             env.set('HDF5_MPI', 'ON')
-            env.set('HDF5_DIR', self.spec['hdf5'].prefix)
 
     @when('@3.0.0:')
     def configure(self, spec, prefix):