diff --git a/quiche/quic/core/quic_session.cc b/quiche/quic/core/quic_session.cc
index a804c47..ec01c2c 100644
--- a/quiche/quic/core/quic_session.cc
+++ b/quiche/quic/core/quic_session.cc
@@ -2333,17 +2333,19 @@
          num_zombie_streams_;
 }
 
-void QuicSession::MarkConnectionLevelWriteBlocked(QuicStreamId id) {
+bool QuicSession::MarkConnectionLevelWriteBlocked(QuicStreamId id) {
+  bool ok = true;
   if (GetOrCreateStream(id) == nullptr) {
+    ok = false;
     QUIC_BUG(quic_bug_10866_11)
         << "Marking unknown stream " << id << " blocked.";
-    QUIC_LOG_FIRST_N(ERROR, 2) << QuicStackTrace();
   }
 
   QUIC_DVLOG(1) << ENDPOINT << "Adding stream " << id
                 << " to write-blocked list";
 
   write_blocked_streams_->AddStream(id);
+  return ok;
 }
 
 bool QuicSession::HasDataToWrite() const {
diff --git a/quiche/quic/core/quic_session.h b/quiche/quic/core/quic_session.h
index 23537f0..e50e185 100644
--- a/quiche/quic/core/quic_session.h
+++ b/quiche/quic/core/quic_session.h
@@ -410,7 +410,9 @@
   // connection-level flow control but not by its own stream-level flow control.
   // The stream will be given a chance to write when a connection-level
   // WINDOW_UPDATE arrives.
-  virtual void MarkConnectionLevelWriteBlocked(QuicStreamId id);
+  // TODO(b/235204908) Remove the return value.
+  // Returns false if an error occurred.
+  bool MarkConnectionLevelWriteBlocked(QuicStreamId id);
 
   // Called to close zombie stream |id|.
   void MaybeCloseZombieStream(QuicStreamId id);