diff --git a/tests/testing-resources/include/aws/testing/mocks/monitoring/TestingMonitoring.h b/tests/testing-resources/include/aws/testing/mocks/monitoring/TestingMonitoring.h
index 0902b72d632..177c9ef65f9 100644
--- a/tests/testing-resources/include/aws/testing/mocks/monitoring/TestingMonitoring.h
+++ b/tests/testing-resources/include/aws/testing/mocks/monitoring/TestingMonitoring.h
@@ -83,6 +83,8 @@ class TestingMonitoring : public Aws::Monitoring::MonitoringInterface
         AWS_UNREFERENCED_PARAM(serviceName);
         AWS_UNREFERENCED_PARAM(requestName);
         AWS_UNREFERENCED_PARAM(context);
+        std::unique_lock<std::mutex> locker(s_lastMutex);
+
         TestingMonitoringMetrics::s_lastUriString = request->GetUri().GetURIString().c_str();
         TestingMonitoringMetrics::s_lastSigningRegion = request->GetSigningRegion().c_str();
         Aws::Vector<Aws::String> authComponents = request->HasAwsAuthorization() ?
@@ -155,6 +157,7 @@ class TestingMonitoringManager
 private:
     static void Init()
     {
+        std::unique_lock<std::mutex> locker(s_lastMutex);
         TestingMonitoringMetrics::Config::s_enablePayload = false;
 
         TestingMonitoringMetrics::s_lastUriString = "";