diff --git a/var/spack/repos/builtin/packages/laghos/package.py b/var/spack/repos/builtin/packages/laghos/package.py
index e14f0591a14f4849f00c386f4772a4aa5e447093..3b6e23307c8898d1bc264813c26253d85c23958a 100644
--- a/var/spack/repos/builtin/packages/laghos/package.py
+++ b/var/spack/repos/builtin/packages/laghos/package.py
@@ -53,6 +53,7 @@ def build_targets(self):
                        'share/mfem/config.mk'))
         targets.append('TEST_MK=%s' % join_path(spec['mfem'].prefix,
                        'share/mfem/test.mk'))
+        targets.append('CXX=%s' % spec['mpi'].mpicxx)
 
         return targets