diff --git a/hub_test.go b/hub_test.go
index 654ed00..ff44955 100644
--- a/hub_test.go
+++ b/hub_test.go
@@ -1933,6 +1933,9 @@ func TestClientMessageToSessionIdWhileDisconnected(t *testing.T) {
 	client1.SendMessage(recipient2, data1) // nolint
 	client1.SendMessage(recipient2, data1) // nolint
 
+	// Simulate some time until client resumes the session.
+	time.Sleep(10 * time.Millisecond)
+
 	client2 = NewTestClient(t, server, hub)
 	defer client2.CloseWithBye()
 	if err := client2.SendHelloResume(hello2.Hello.ResumeId); err != nil {
diff --git a/natsclient_loopback.go b/natsclient_loopback.go
index 12fb8db..e9c33d7 100644
--- a/natsclient_loopback.go
+++ b/natsclient_loopback.go
@@ -25,6 +25,7 @@ import (
 	"encoding/json"
 	"strings"
 	"sync"
+	"time"
 
 	"github.com/nats-io/nats.go"
 )
@@ -95,6 +96,9 @@ func (s *loopbackNatsSubscription) run() {
 			msg := s.incoming[0]
 			s.incoming = s.incoming[1:]
 			s.cond.L.Unlock()
+			// A "real" NATS server would take some time to process the request,
+			// simulate this by sleeping a tiny bit.
+			time.Sleep(time.Millisecond)
 			s.ch <- msg
 			s.cond.L.Lock()
 		}