diff --git a/test/echo.py b/test/echo.py
index b781c19..d51191a 100644
--- a/test/echo.py
+++ b/test/echo.py
@@ -114,7 +114,7 @@ def run(self):
             rms_data_db = []
             for ch in range(self.channels):
                 mono = data[ch::self.channels]
-                self.kws_list[ch].put(mono.tostring())
+                self.kws_list[ch].put(mono.tobytes())
 
 
 def main():
diff --git a/tuning.py b/tuning.py
index 0272329..3adef75 100755
--- a/tuning.py
+++ b/tuning.py
@@ -106,7 +106,7 @@ def read(self, name):
             usb.util.CTRL_IN | usb.util.CTRL_TYPE_VENDOR | usb.util.CTRL_RECIPIENT_DEVICE,
             0, cmd, id, length, self.TIMEOUT)
 
-        response = struct.unpack(b'ii', response.tostring())
+        response = struct.unpack(b'ii', response.tobytes())
 
         if data[2] == 'int':
             result = response[0]