diff --git a/var/spack/repos/builtin/packages/mfem/package.py b/var/spack/repos/builtin/packages/mfem/package.py
index a04c5bb4ce8..22b344a28b3 100644
--- a/var/spack/repos/builtin/packages/mfem/package.py
+++ b/var/spack/repos/builtin/packages/mfem/package.py
@@ -697,6 +697,9 @@ def install(self, spec, prefix):
         if install_em:
             install_tree('data', join_path(prefix_share, 'data'))
 
+    # The files referenced in this patch method do not exist in stable
+    # versions earlier than 4.1.
+    @when('@4.1:')
     def patch(self):
         # Remove the byte order mark since it messes with some compilers
         filter_file(u'\uFEFF', '', 'fem/gslib.hpp')