diff --git a/modules/video_coding/codecs/vp9/vp9_impl.cc b/modules/video_coding/codecs/vp9/vp9_impl.cc
index cf2d37000d..b0dc108daa 100644
--- a/modules/video_coding/codecs/vp9/vp9_impl.cc
+++ b/modules/video_coding/codecs/vp9/vp9_impl.cc
@@ -582,10 +582,11 @@ int VP9EncoderImpl::InitEncode(const VideoCodec* inst,
 
   // External reference control is required for different frame rate on spatial
   // layers because libvpx generates rtp incompatible references in this case.
-  external_ref_control_ = field_trial::IsEnabled("WebRTC-Vp9ExternalRefCtrl") ||
-                          (num_spatial_layers_ > 1 &&
-                           codec_.mode == VideoCodecMode::kScreensharing) ||
-                          inter_layer_pred_ == InterLayerPredMode::kOn;
+  external_ref_control_ =
+      !field_trial::IsDisabled("WebRTC-Vp9ExternalRefCtrl") ||
+      (num_spatial_layers_ > 1 &&
+       codec_.mode == VideoCodecMode::kScreensharing) ||
+      inter_layer_pred_ == InterLayerPredMode::kOn;
 
   if (num_temporal_layers_ == 1) {
     gof_.SetGofInfoVP9(kTemporalStructureMode1);