diff --git a/api/media_stream_interface.h b/api/media_stream_interface.h
index 1249b85..ccacb4c 100644
--- a/api/media_stream_interface.h
+++ b/api/media_stream_interface.h
@@ -30,6 +30,7 @@
 #include "api/video/video_source_interface.h"
 #include "modules/audio_processing/include/audio_processing_statistics.h"
 #include "rtc_base/ref_count.h"
+#include "rtc_base/system/rtc_export.h"
 
 namespace webrtc {
 
@@ -52,8 +53,8 @@
 
 // Base class for sources. A MediaStreamTrack has an underlying source that
 // provides media. A source can be shared by multiple tracks.
-class MediaSourceInterface : public rtc::RefCountInterface,
-                             public NotifierInterface {
+class RTC_EXPORT MediaSourceInterface : public rtc::RefCountInterface,
+                                        public NotifierInterface {
  public:
   enum SourceState { kInitializing, kLive, kEnded, kMuted };
 
@@ -74,8 +75,8 @@
 
 // C++ version of MediaStreamTrack.
 // See: https://www.w3.org/TR/mediacapture-streams/#mediastreamtrack
-class MediaStreamTrackInterface : public rtc::RefCountInterface,
-                                  public NotifierInterface {
+class RTC_EXPORT MediaStreamTrackInterface : public rtc::RefCountInterface,
+                                             public NotifierInterface {
  public:
   enum TrackState {
     kLive,
@@ -190,7 +191,7 @@
 
 // AudioSourceInterface is a reference counted source used for AudioTracks.
 // The same source can be used by multiple AudioTracks.
-class AudioSourceInterface : public MediaSourceInterface {
+class RTC_EXPORT AudioSourceInterface : public MediaSourceInterface {
  public:
   class AudioObserver {
    public: