diff --git a/greenctld b/greenctld
index 4f1e2f2..b7a94d5 100755
--- a/greenctld
+++ b/greenctld
@@ -58,8 +58,8 @@ class GreenHeronRotor(object):
 
     def stop(self):
         print("==> Stop")
-        self.az_serial.write(';')
-        self.el_serial.write(';')
+        self.az_serial.write(';'.encode('utf-8'))
+        self.el_serial.write(';'.encode('utf-8'))
 
     def set_pos(self, az, el):
         print('==> %d,%d' % (az, el))