diff --git a/avs/player/mpg123_player.py b/avs/player/mpg123_player.py
index 0974190..3784241 100644
--- a/avs/player/mpg123_player.py
+++ b/avs/player/mpg123_player.py
@@ -47,26 +47,26 @@ def play(self, uri):
         self.event.set()
 
         if self.process and self.process.poll() == None:
-            os.write(self.tty, 'q')
+            os.write(self.tty, b'q')
 
         self.state = 'PLAYING'
 
     def stop(self):
         if self.process and self.process.poll() == None:
-            os.write(self.tty, 'q')
+            os.write(self.tty, b'q')
         self.state = 'NULL'
 
     def pause(self):
         if self.state == 'PLAYING':
             self.state = 'PAUSED'
-            os.write(self.tty, 's')
+            os.write(self.tty, b's')
 
         print('pause()')
 
     def resume(self):
         if self.state == 'PAUSED':
             self.state = 'PLAYING'
-            os.write(self.tty, 's')
+            os.write(self.tty, b's')
 
     # name: {eos, ...}
     def add_callback(self, name, callback):
diff --git a/avs/player/mpv_player.py b/avs/player/mpv_player.py
index 60f5d95..1272c5f 100644
--- a/avs/player/mpv_player.py
+++ b/avs/player/mpv_player.py
@@ -44,13 +44,13 @@ def play(self, uri):
         self.event.set()
 
         if self.process and self.process.poll() == None:
-            os.write(self.tty, 'q')
+            os.write(self.tty, b'q')
 
         self.state = 'PLAYING'
 
     def stop(self):
         if self.process and self.process.poll() == None:
-            os.write(self.tty, 'q')
+            os.write(self.tty, b'q')
         self.state = 'NULL'
 
     def pause(self):
@@ -63,7 +63,7 @@ def pause(self):
     def resume(self):
         if self.state == 'PAUSED':
             self.state = 'PLAYING'
-            os.write(self.tty, ' ')
+            os.write(self.tty, b' ')
 
     # name: {eos, ...}
     def add_callback(self, name, callback):