diff --git a/var/spack/repos/builtin/packages/openmx/package.py b/var/spack/repos/builtin/packages/openmx/package.py
index 05d16d36fe5..ddcd7e4e033 100644
--- a/var/spack/repos/builtin/packages/openmx/package.py
+++ b/var/spack/repos/builtin/packages/openmx/package.py
@@ -79,7 +79,7 @@ def common_arguments(self):
         if "%fj" in spec:
             common_option.append("-Dkcomp  -Kfast")
             cc_option.append("-Dnosse -Nclang")
-            fc_option.append(self.compiler.openmp_flag)
+            fc_option.extend([self.compiler.openmp_flag, "-Ccpp"])
         else:
             common_option.append("-O3")
             if "%gcc" in spec: