diff --git a/test/server.ts b/test/server.ts
index 4df99df4..5c853a39 100644
--- a/test/server.ts
+++ b/test/server.ts
@@ -594,6 +594,7 @@ describe('server', function () {
         })
 
         it('should not retry sending the response', function (done) {
+            clock = sinon.useFakeTimers()
             let messages = 0
 
             send(generate(packet))
@@ -652,6 +653,7 @@ describe('server', function () {
         })
 
         it('should reply with a confirmable after an ack', function (done) {
+            clock = sinon.useFakeTimers()
             send(generate(packet))
             server.on('request', (req, res) => {
                 setTimeout(() => {
@@ -676,6 +678,7 @@ describe('server', function () {
         })
 
         it('should retry sending the response if it does not receive an ack four times before 45s', function (done) {
+            clock = sinon.useFakeTimers()
             let messages = 0
 
             send(generate(packet))
@@ -706,6 +709,7 @@ describe('server', function () {
         })
 
         it('should stop resending after it receives an ack', function (done) {
+            clock = sinon.useFakeTimers()
             let messages = 0
 
             send(generate(packet))
@@ -736,6 +740,7 @@ describe('server', function () {
         })
 
         it('should not resend with a piggyback response', function (done) {
+            clock = sinon.useFakeTimers()
             let messages = 0
 
             send(generate(packet))
@@ -756,6 +761,7 @@ describe('server', function () {
         })
 
         it('should error if it does not receive an ack four times before ~247s', function (done) {
+            clock = sinon.useFakeTimers()
             send(generate(packet))
             server.on('request', (req, res) => {
                 // needed to avoid sending a piggyback response
@@ -877,6 +883,8 @@ describe('server', function () {
         })
 
         it('should emit a \'finish\' if the client do not ack for ~247s', function (done) {
+            clock = sinon.useFakeTimers()
+
             doObserve()
 
             server.on('request', (req, res) => {