diff --git a/geometry/graham_scan_algorithm.cpp b/geometry/graham_scan_algorithm.cpp
index 426751e85..06c1c0ec6 100644
--- a/geometry/graham_scan_algorithm.cpp
+++ b/geometry/graham_scan_algorithm.cpp
@@ -43,7 +43,7 @@
  * @brief Self-test implementations
  * @returns void
  *******************************************************************************/
-void test() {
+static void test() {
     std::vector<geometry::grahamscan::Point> points = {{0, 3},
                                                        {1, 1},
                                                        {2, 2},