diff --git a/media/sctp/dcsctp_transport.cc b/media/sctp/dcsctp_transport.cc
index 7b7ce5f18b..525075468c 100644
--- a/media/sctp/dcsctp_transport.cc
+++ b/media/sctp/dcsctp_transport.cc
@@ -349,6 +349,7 @@ RTCError DcSctpTransport::SendData(int sid,
 }
 
 bool DcSctpTransport::ReadyToSendData() {
+  RTC_DCHECK_RUN_ON(network_thread_);
   return ready_to_send_data_;
 }
 
@@ -511,6 +512,7 @@ void DcSctpTransport::OnConnected() {
 }
 
 void DcSctpTransport::OnClosed() {
+  RTC_DCHECK_RUN_ON(network_thread_);
   RTC_DLOG(LS_INFO) << debug_name_ << "->OnClosed().";
   ready_to_send_data_ = false;
 }
diff --git a/media/sctp/dcsctp_transport.h b/media/sctp/dcsctp_transport.h
index 84ae36fa3b..7ae0d64134 100644
--- a/media/sctp/dcsctp_transport.h
+++ b/media/sctp/dcsctp_transport.h
@@ -131,7 +131,7 @@ class DcSctpTransport : public cricket::SctpTransportInternal,
   // Map of all currently open or closing data channels
   flat_map<dcsctp::StreamID, StreamState> stream_states_
       RTC_GUARDED_BY(network_thread_);
-  bool ready_to_send_data_ = false;
+  bool ready_to_send_data_ RTC_GUARDED_BY(network_thread_) = false;
   std::function<void()> on_connected_callback_ RTC_GUARDED_BY(network_thread_);
   DataChannelSink* data_channel_sink_ RTC_GUARDED_BY(network_thread_) = nullptr;
 };