diff --git a/x-pack/plugins/apm/server/utils/with_span.ts b/x-pack/plugins/apm/server/utils/with_span.ts
index be3279772d1df..b0c07fac4a0fe 100644
--- a/x-pack/plugins/apm/server/utils/with_span.ts
+++ b/x-pack/plugins/apm/server/utils/with_span.ts
@@ -43,6 +43,7 @@ export function withSpan<T>(
   const resource = new asyncHooks.AsyncResource('fake_async');
 
   return resource.runInAsyncScope(() => {
+    // set the active span for the newly created async context
     // @ts-ignore
     agent._instrumentation.activeSpan = span;
     if (type) {