diff --git a/lib/internal/test_runner/harness.js b/lib/internal/test_runner/harness.js
index 202759bdbfe7ae..5f43e846f29585 100644
--- a/lib/internal/test_runner/harness.js
+++ b/lib/internal/test_runner/harness.js
@@ -225,7 +225,11 @@ function getGlobalRoot() {
 }
 
 async function startSubtest(subtest) {
-  await reportersSetup;
+  if (reportersSetup) {
+    // Only incur the overhead of awaiting the Promise once.
+    await reportersSetup;
+    reportersSetup = undefined;
+  }
 
   const root = getGlobalRoot();
   if (!root.harness.bootstrapComplete) {