diff --git a/rxjava-core/src/main/java/rx/observers/TestSubscriber.java b/rxjava-core/src/main/java/rx/observers/TestSubscriber.java
index 97966b8ebd..dd1f2b8a7e 100644
--- a/rxjava-core/src/main/java/rx/observers/TestSubscriber.java
+++ b/rxjava-core/src/main/java/rx/observers/TestSubscriber.java
@@ -64,6 +64,7 @@ public void onNext(T t) {
     @Override
     public void onCompleted() {
         try {
+            lastSeenThread = Thread.currentThread();
             testObserver.onCompleted();
         } finally {
             latch.countDown();
@@ -77,6 +78,7 @@ public List<Notification<T>> getOnCompletedEvents() {
     @Override
     public void onError(Throwable e) {
         try {
+            lastSeenThread = Thread.currentThread();
             testObserver.onError(e);
         } finally {
             latch.countDown();