diff --git a/media/video/vpx_video_encoder.cc b/media/video/vpx_video_encoder.cc
index e80e08ae5a07023e277f2b7c8cd9cf5e35afd74b..be74c74fc053afd3718f21b0c571701b280ef574 100644
--- a/media/video/vpx_video_encoder.cc
+++ b/media/video/vpx_video_encoder.cc
@@ -614,6 +614,10 @@ void VpxVideoEncoder::ChangeOptions(const Options& options,
     std::move(done_cb).Run(status);
     return;
   }
+  
+  // libvpx doesn't support adjusting the number of threads
+  // midway through an encoding session. More details: crbug.com/1486441
+  new_config.g_threads = codec_config_.g_threads;
 
   status = ReallocateVpxImageIfNeeded(&vpx_image_, vpx_image_.fmt,
                                       options.frame_size.width(),