diff --git a/pc/channel.cc b/pc/channel.cc
index 9e113c819f..b85122d922 100644
--- a/pc/channel.cc
+++ b/pc/channel.cc
@@ -133,7 +133,16 @@ BaseChannel::BaseChannel(rtc::Thread* worker_thread,
       ssrc_generator_(ssrc_generator) {
   RTC_DCHECK_RUN_ON(worker_thread_);
   RTC_DCHECK(ssrc_generator_);
-  demuxer_criteria_.mid = content_name;
+  // Temp fix: MID in SDP is allowed to be slightly longer than what's allowed
+  // in the RTP demuxer. Truncate if needed; this won't match, but it only
+  // makes sense in places that wouldn't use this for matching anyway.
+  // TODO(bugs.webrtc.org/12517): remove when length 16 is policed by parser.
+  if (content_name.size() > 16) {
+    RTC_LOG(LS_ERROR) << "Overlong mid attribute, truncating for matching";
+    demuxer_criteria_.mid = content_name.substr(0, 16);
+  } else {
+    demuxer_criteria_.mid = content_name;
+  }
   RTC_LOG(LS_INFO) << "Created channel: " << ToString();
 }