diff --git a/processor_test.go b/processor_test.go
index 9ecb8fe..da1b577 100644
--- a/processor_test.go
+++ b/processor_test.go
@@ -104,12 +104,14 @@ func TestProcessorSuccess(t *testing.T) {
 				t.Fatal(err)
 			}
 		}
-		time.Sleep(time.Second) // wait for one second to allow all enqueued tasks to be processed.
+		time.Sleep(2 * time.Second) // wait for two second to allow all enqueued tasks to be processed.
 		p.terminate()
 
+		mu.Lock()
 		if diff := cmp.Diff(tc.wantProcessed, processed, sortTaskOpt, cmp.AllowUnexported(Payload{})); diff != "" {
 			t.Errorf("mismatch found in processed tasks; (-want, +got)\n%s", diff)
 		}
+		mu.Unlock()
 
 		if l := r.LLen(base.InProgressQueue).Val(); l != 0 {
 			t.Errorf("%q has %d tasks, want 0", base.InProgressQueue, l)
@@ -160,7 +162,7 @@ func TestProcessorRetry(t *testing.T) {
 			handler: HandlerFunc(func(ctx context.Context, task *Task) error {
 				return fmt.Errorf(errMsg)
 			}),
-			wait: time.Second,
+			wait: 2 * time.Second,
 			wantRetry: []h.ZSetEntry{
 				{Msg: &r2, Score: float64(now.Add(time.Minute).Unix())},
 				{Msg: &r3, Score: float64(now.Add(time.Minute).Unix())},
@@ -217,7 +219,7 @@ func TestProcessorRetry(t *testing.T) {
 				t.Fatal(err)
 			}
 		}
-		time.Sleep(tc.wait)
+		time.Sleep(tc.wait) // FIXME: This makes test flaky.
 		p.terminate()
 
 		cmpOpt := cmpopts.EquateApprox(0, float64(time.Second)) // allow up to a second difference in zset score