diff --git a/example/geographic.cpp b/example/geographic.cpp
index 4df92a14..214775d7 100644
--- a/example/geographic.cpp
+++ b/example/geographic.cpp
@@ -24,6 +24,13 @@
 #include <cmath>
 #include <numbers>
 
+namespace {
+
+using namespace units::physical::si::unit_constants;
+inline constexpr auto earth_radius = 6371 * km;
+
+}  // namespace
+
 namespace geographic {
 
 distance spherical_distance(position from, position to)
diff --git a/example/geographic.h b/example/geographic.h
index 2c00d549..b03eab3b 100644
--- a/example/geographic.h
+++ b/example/geographic.h
@@ -119,9 +119,6 @@ namespace geographic {
 struct horizontal_kind : units::kind<horizontal_kind, units::physical::si::dim_length> {};
 using distance = units::quantity_kind<horizontal_kind, units::physical::si::kilometre>;
 
-using namespace units::physical::si::unit_constants;
-inline constexpr auto earth_radius = 6371 * km;
-
 struct position {
   latitude lat;
   longitude lon;