diff --git a/math/lcm_sum.cpp b/math/lcm_sum.cpp
index 4a317784b..950a90c17 100644
--- a/math/lcm_sum.cpp
+++ b/math/lcm_sum.cpp
@@ -76,7 +76,7 @@ static void test() {
     std::cout << "Passed Test 4!" << std::endl;
 
     n = 15;
-    int test_5 = lcmSum(n);
+    int test_5 = math::lcmSum(n);
     assert(test_5 == 1110);
     std::cout << "Passed Test 5!" << std::endl;
 }