diff --git a/media/webrtc/trunk/webrtc/modules/video_coding/main/source/media_optimization.cc b/media/webrtc/trunk/webrtc/modules/video_coding/main/source/media_optimization.cc
index 3f32ae8e1063..e31939129332 100644
--- a/media/webrtc/trunk/webrtc/modules/video_coding/main/source/media_optimization.cc
+++ b/media/webrtc/trunk/webrtc/modules/video_coding/main/source/media_optimization.cc
@@ -695,6 +695,7 @@ void MediaOptimization::ProcessIncomingFrameRate(int64_t now) {
 }
 
 void MediaOptimization::SetCPULoadState(CPULoadState state) {
+    CriticalSectionScoped lock(crit_sect_.get());
     loadstate_ = state;
 }