diff --git a/system/diagnostic_graph_aggregator/test/src/test2.cpp b/system/diagnostic_graph_aggregator/test/src/test2.cpp
index b010994f5a1ca..6e2fe0fbf0bfb 100644
--- a/system/diagnostic_graph_aggregator/test/src/test2.cpp
+++ b/system/diagnostic_graph_aggregator/test/src/test2.cpp
@@ -26,7 +26,6 @@ using namespace diagnostic_graph_aggregator;  // NOLINT(build/namespaces)
 
 using diagnostic_msgs::msg::DiagnosticArray;
 using diagnostic_msgs::msg::DiagnosticStatus;
-using tier4_system_msgs::msg::DiagnosticGraph;
 
 constexpr auto OK = DiagnosticStatus::OK;
 constexpr auto WARN = DiagnosticStatus::WARN;