diff --git a/modules/video_coding/timing/timing.h b/modules/video_coding/timing/timing.h
index 7a8183d..fc6d87d 100644
--- a/modules/video_coding/timing/timing.h
+++ b/modules/video_coding/timing/timing.h
@@ -23,12 +23,10 @@
 #include "rtc_base/experiments/field_trial_parser.h"
 #include "rtc_base/synchronization/mutex.h"
 #include "rtc_base/thread_annotations.h"
+#include "system_wrappers/include/clock.h"
 
 namespace webrtc {
 
-class Clock;
-class TimestampExtrapolator;
-
 class VCMTiming {
  public:
   static constexpr auto kDefaultRenderDelay = TimeDelta::Millis(10);