diff --git a/src/workerd/api/trace.c++ b/src/workerd/api/trace.c++
index 32abe18d2a8..d25d680a91e 100644
--- a/src/workerd/api/trace.c++
+++ b/src/workerd/api/trace.c++
@@ -611,7 +611,7 @@ kj::Promise<void> sendTracesToExportedHandler(kj::Own<IoContext::IncomingRequest
       jsg::AsyncContextFrame::StorageScope traceScope = context.makeAsyncTraceScope(lock);
 
       auto handler = lock.getExportedHandler(entrypointName, context.getActor());
-      lock.getGlobalScope().sendTraces(traces, lock, handler);
+      return lock.getGlobalScope().sendTraces(traces, lock, handler);
     });
   } catch (kj::Exception e) {
     // TODO(someday): We only report sendTraces() as failed for metrics/logging if the initial
@@ -654,11 +654,10 @@ auto TraceCustomEventImpl::sendRpc(capnp::HttpOverCapnpFactory& httpOverCapnpFac
     traces[i]->copyTo(out[i]);
   }
 
-  waitUntilTasks.add(req.send().ignoreResult());
-
-  // As long as we sent it, we consider the result to be okay.
-  co_return Result{
-    .outcome = workerd::EventOutcome::OK,
+  auto resp = co_await req.send();
+  auto respResult = resp.getResult();
+  co_return WorkerInterface::CustomEvent::Result{
+    .outcome = respResult.getOutcome(),
   };
 }
 
diff --git a/src/workerd/io/worker-interface.capnp b/src/workerd/io/worker-interface.capnp
index 699f3bcbf8e..bda40634e96 100644
--- a/src/workerd/io/worker-interface.capnp
+++ b/src/workerd/io/worker-interface.capnp
@@ -140,6 +140,10 @@ struct Trace @0x8e8d911203762d34 {
   # Indicates that the trace was truncated due to reaching the maximum size limit.
 }
 
+struct SendTracesRun @0xde913ebe8e1b82a5 {
+  outcome @0 :EventOutcome;
+}
+
 struct ScheduledRun @0xd98fc1ae5c8095d0 {
   outcome @0 :EventOutcome;
 
@@ -404,7 +408,7 @@ interface EventDispatcher @0xf20697475ec1752d {
   getHttpService @0 () -> (http :HttpService) $Cxx.allowCancellation;
   # Gets the HTTP interface to this worker (to trigger FetchEvents).
 
-  sendTraces @1 (traces :List(Trace)) $Cxx.allowCancellation;
+  sendTraces @1 (traces :List(Trace)) -> (result :SendTracesRun) $Cxx.allowCancellation;
   # Deliver a trace event to a trace worker. This always completes immediately; the trace handler
   # runs as a "waitUntil" task.
 
diff --git a/src/workerd/io/worker-interface.h b/src/workerd/io/worker-interface.h
index 6ad10b820ac..ff7ca2db705 100644
--- a/src/workerd/io/worker-interface.h
+++ b/src/workerd/io/worker-interface.h
@@ -149,7 +149,7 @@ class WorkerInterface: public kj::HttpService {
 // for the promise, then invoke the destination object.
 kj::Own<WorkerInterface> newPromisedWorkerInterface(
     kj::TaskSet& waitUntilTasks, kj::Promise<kj::Own<WorkerInterface>> promise);
-// TODO(cleanup): `waitUntilTasks` is only needed to handle `sendTraces` and `prewarm` since they
+// TODO(cleanup): `waitUntilTasks` is only needed to handle `prewarm` since they
 //   don't return promises. We should maybe change them to return promises?
 
 // Adapts WorkerInterface to HttpClient, including taking ownership.