diff --git a/var/spack/repos/builtin/packages/root/package.py b/var/spack/repos/builtin/packages/root/package.py
index 4d80d1235a51a6b546076d1dd0d26e048e9cffec..9d0f4937ffb628200de86b5b8508257c0886f243 100644
--- a/var/spack/repos/builtin/packages/root/package.py
+++ b/var/spack/repos/builtin/packages/root/package.py
@@ -463,6 +463,7 @@ def cmake_args(self):
 
     def setup_environment(self, spack_env, run_env):
         run_env.prepend_path('PYTHONPATH', self.prefix.lib)
+        spack_env.set('SPACK_INCLUDE_DIRS', '')
 
     def setup_dependent_environment(self, spack_env, run_env, dependent_spec):
         spack_env.set('ROOTSYS', self.prefix)