diff --git a/pkg/controller/certificates/controller.go b/pkg/controller/certificates/controller.go
index 1ea21a8fe..000de0acf 100644
--- a/pkg/controller/certificates/controller.go
+++ b/pkg/controller/certificates/controller.go
@@ -119,13 +119,13 @@ func (c *certificateRequestManager) Register(ctx *controllerpkg.Context) (workqu
 	certificateRequestInformer.Informer().AddEventHandler(&controllerpkg.BlockingEventHandler{WorkFunc: controllerpkg.HandleOwnedResourceNamespacedFunc(log, c.queue, certificateGvk, certificateGetter(c.certificateLister))})
 	secretsInformer.Informer().AddEventHandler(&controllerpkg.BlockingEventHandler{WorkFunc: secretResourceHandler(log, c.certificateLister, c.queue)})
 
+	// clock is used to determine whether certificates need renewal
+	c.clock = ctx.Clock
+
 	// Create a scheduled work queue that calls the ctrl.queue.Add method for
 	// each object in the queue. This is used to schedule re-checks of
 	// Certificate resources when they get near to expiry
-	c.scheduledWorkQueue = scheduler.NewScheduledWorkQueue(c.queue.Add)
-
-	// clock is used to determine whether certificates need renewal
-	c.clock = clock.RealClock{}
+	c.scheduledWorkQueue = scheduler.NewScheduledWorkQueue(c.clock, c.queue.Add)
 
 	// recorder records events about resources to the Kubernetes api
 	c.recorder = ctx.Recorder
diff --git a/pkg/scheduler/BUILD.bazel b/pkg/scheduler/BUILD.bazel
index 20810b4c4..fbc03a1cb 100644
--- a/pkg/scheduler/BUILD.bazel
+++ b/pkg/scheduler/BUILD.bazel
@@ -5,12 +5,14 @@ go_library(
     srcs = ["scheduler.go"],
     importpath = "github.com/jetstack/cert-manager/pkg/scheduler",
     visibility = ["//visibility:public"],
+    deps = ["@io_k8s_utils//clock:go_default_library"],
 )
 
 go_test(
     name = "go_default_test",
     srcs = ["scheduler_test.go"],
     embed = [":go_default_library"],
+    deps = ["@io_k8s_utils//clock:go_default_library"],
 )
 
 filegroup(
diff --git a/pkg/scheduler/scheduler.go b/pkg/scheduler/scheduler.go
index 7142a56ee..b31e5dbb7 100644
--- a/pkg/scheduler/scheduler.go
+++ b/pkg/scheduler/scheduler.go
@@ -19,14 +19,26 @@ package scheduler
 import (
 	"sync"
 	"time"
+
+	"k8s.io/utils/clock"
 )
 
 // For mocking purposes.
 // This little bit of wrapping needs to be done because go doesn't do
 // covariance, but it does coerce *time.Timer into stoppable implicitly if we
 // write it out like so.
-var afterFunc = func(d time.Duration, f func()) stoppable {
-	return time.AfterFunc(d, f)
+var afterFunc = func(c clock.Clock, d time.Duration, f func()) stoppable {
+	t := c.NewTimer(d)
+
+	go func() {
+		defer t.Stop()
+		if ti := <-t.C(); ti == (time.Time{}) {
+			return
+		}
+		f()
+	}()
+
+	return t
 }
 
 // stoppable is the subset of time.Timer which we use, split out for mocking purposes
@@ -51,13 +63,19 @@ type ScheduledWorkQueue interface {
 
 type scheduledWorkQueue struct {
 	processFunc ProcessFunc
+	clock       clock.Clock
 	work        map[interface{}]stoppable
 	workLock    sync.Mutex
 }
 
 // NewScheduledWorkQueue will create a new workqueue with the given processFunc
-func NewScheduledWorkQueue(processFunc ProcessFunc) ScheduledWorkQueue {
-	return &scheduledWorkQueue{processFunc, make(map[interface{}]stoppable), sync.Mutex{}}
+func NewScheduledWorkQueue(clock clock.Clock, processFunc ProcessFunc) ScheduledWorkQueue {
+	return &scheduledWorkQueue{
+		processFunc: processFunc,
+		clock:       clock,
+		work:        make(map[interface{}]stoppable),
+		workLock:    sync.Mutex{},
+	}
 }
 
 // Add will add an item to this queue, executing the ProcessFunc after the
@@ -67,7 +85,7 @@ func (s *scheduledWorkQueue) Add(obj interface{}, duration time.Duration) {
 	s.workLock.Lock()
 	defer s.workLock.Unlock()
 	s.forget(obj)
-	s.work[obj] = afterFunc(duration, func() {
+	s.work[obj] = afterFunc(s.clock, duration, func() {
 		defer s.Forget(obj)
 		s.processFunc(obj)
 	})
diff --git a/pkg/scheduler/scheduler_test.go b/pkg/scheduler/scheduler_test.go
index 06d7c900d..33cfd1b1f 100644
--- a/pkg/scheduler/scheduler_test.go
+++ b/pkg/scheduler/scheduler_test.go
@@ -20,6 +20,8 @@ import (
 	"sync"
 	"testing"
 	"time"
+
+	"k8s.io/utils/clock"
 )
 
 func TestAdd(t *testing.T) {
@@ -42,7 +44,7 @@ func TestAdd(t *testing.T) {
 			waitSubtest := make(chan struct{})
 			return func(t *testing.T) {
 				startTime := after.currentTime
-				queue := NewScheduledWorkQueue(func(obj interface{}) {
+				queue := NewScheduledWorkQueue(clock.RealClock{}, func(obj interface{}) {
 					defer wg.Done()
 					durationEarly := test.duration - after.currentTime.Sub(startTime)
 
@@ -83,7 +85,7 @@ func TestForget(t *testing.T) {
 		t.Run(test.obj, func(test testT) func(*testing.T) {
 			return func(t *testing.T) {
 				defer wg.Done()
-				queue := NewScheduledWorkQueue(func(obj interface{}) {
+				queue := NewScheduledWorkQueue(clock.RealClock{}, func(obj interface{}) {
 					t.Errorf("scheduled function should never be called")
 				})
 				queue.Add(test.obj, test.duration)
@@ -102,7 +104,7 @@ func TestConcurrentAdd(t *testing.T) {
 	after := newMockAfter()
 	afterFunc = after.AfterFunc
 	var wg sync.WaitGroup
-	queue := NewScheduledWorkQueue(func(obj interface{}) {
+	queue := NewScheduledWorkQueue(clock.RealClock{}, func(obj interface{}) {
 		t.Fatalf("should not be called, but was called with %v", obj)
 	})
 
@@ -146,7 +148,7 @@ func newMockAfter() *mockAfter {
 	}
 }
 
-func (m *mockAfter) AfterFunc(d time.Duration, f func()) stoppable {
+func (m *mockAfter) AfterFunc(c clock.Clock, d time.Duration, f func()) stoppable {
 	m.lock.Lock()
 	defer m.lock.Unlock()