diff --git a/include/xo/unit/basis_unit.hpp b/include/xo/unit/mpl/basis_unit.hpp
similarity index 100%
rename from include/xo/unit/basis_unit.hpp
rename to include/xo/unit/mpl/basis_unit.hpp
diff --git a/include/xo/unit/ratio_concept.hpp b/include/xo/unit/mpl/ratio_concept.hpp
similarity index 100%
rename from include/xo/unit/ratio_concept.hpp
rename to include/xo/unit/mpl/ratio_concept.hpp
diff --git a/include/xo/unit/ratio_util.hpp b/include/xo/unit/mpl/ratio_util.hpp
similarity index 100%
rename from include/xo/unit/ratio_util.hpp
rename to include/xo/unit/mpl/ratio_util.hpp