diff --git a/README.md b/README.md
index 5f7c127cb2..227fac2de3 100755
--- a/README.md
+++ b/README.md
@@ -174,6 +174,7 @@ The ports used by SRS:
 
 ## V4 changes
 
+* v4.0, 2021-05-21, Fix [#2370][bug #2370] bug for Firefox play stream(published by Chrome). 4.0.121
 * v4.0, 2021-05-21, RTC: Refine sdk, migrate from onaddstream to ontrack. 4.0.120
 * v4.0, 2021-05-21, Tools: Refine configure options. 4.0.119
 * v4.0, 2021-05-20, Fix build fail when disable RTC by --rtc=off. 4.0.118
@@ -1917,6 +1918,7 @@ Winlin
 [bug #2355]: https://github.com/ossrs/srs/issues/2355
 [bug #307]: https://github.com/ossrs/srs/issues/307
 [bug #2362]: https://github.com/ossrs/srs/issues/2362
+[bug #2370]: https://github.com/ossrs/srs/issues/2370
 [bug #yyyyyyyyyyyyy]: https://github.com/ossrs/srs/issues/yyyyyyyyyyyyy
 
 [bug #1631]: https://github.com/ossrs/srs/issues/1631
diff --git a/trunk/src/app/srs_app_rtc_conn.cpp b/trunk/src/app/srs_app_rtc_conn.cpp
index d1ac732eb0..df57905453 100644
--- a/trunk/src/app/srs_app_rtc_conn.cpp
+++ b/trunk/src/app/srs_app_rtc_conn.cpp
@@ -3121,6 +3121,10 @@ srs_error_t SrsRtcConnection::negotiate_play_capability(SrsRtcUserConfig* ruc, s
         for (int j = 0; j < (int)track_descs.size(); ++j) {
             SrsRtcTrackDescription* track = track_descs.at(j)->copy();
 
+            // We should clear the extmaps of source(publisher).
+            // @see https://github.com/ossrs/srs/issues/2370
+            track->extmaps_.clear();
+
             // Use remote/source/offer PayloadType.
             track->media_->pt_of_publisher_ = track->media_->pt_;
             track->media_->pt_ = remote_payload.payload_type_;
diff --git a/trunk/src/core/srs_core_version4.hpp b/trunk/src/core/srs_core_version4.hpp
index f4e0917d02..44eec8dc1f 100644
--- a/trunk/src/core/srs_core_version4.hpp
+++ b/trunk/src/core/srs_core_version4.hpp
@@ -26,6 +26,6 @@
 
 #define VERSION_MAJOR       4
 #define VERSION_MINOR       0
-#define VERSION_REVISION    120
+#define VERSION_REVISION    121
 
 #endif