diff --git a/raspberry/roberto/Serial.py b/raspberry/roberto/Serial.py
index c5c3d08..8de2b65 100644
--- a/raspberry/roberto/Serial.py
+++ b/raspberry/roberto/Serial.py
@@ -49,12 +49,12 @@ class Serial(object):
                 if data:
                     print(data)
                     command = data[0]
-                    argument = data[2:]
-                    if command in data:
+                    argument = data[2:].strip()
+                    if isalnum(command) and command in self._callbacks:
                         cb = self._callbacks[command]
                         if cb:
                             cb(argument)
-                        
+
         except serial.SerialException:
             pass
             #self.alive = False