--- asynchat.py	2010-09-15 23:08:22.000000000 +0600
+++ asynchat.py	2011-02-26 16:05:18.281822396 +0500
@@ -94,6 +94,8 @@
 
     def set_terminator (self, term):
         "Set the input delimiter.  Can be a fixed string of any length, an integer, or None"
+        if (isinstance(term, int) or isinstance(term, long)) and term < 0:
+            raise ValueError('Negative terminator value is not allowed')
         self.terminator = term
 
     def get_terminator (self):
@@ -121,7 +123,7 @@
 
         while self.ac_in_buffer:
             lb = len(self.ac_in_buffer)
-            terminator = self.get_terminator()
+            terminator = self.terminator
             if not terminator:
                 # no terminator, collect it all
                 self.collect_incoming_data (self.ac_in_buffer)
@@ -132,7 +134,7 @@
                 if lb < n:
                     self.collect_incoming_data (self.ac_in_buffer)
                     self.ac_in_buffer = ''
-                    self.terminator = self.terminator - lb
+                    self.terminator -= lb
                 else:
                     self.collect_incoming_data (self.ac_in_buffer[:n])
                     self.ac_in_buffer = self.ac_in_buffer[n:]