diff --git a/asterisk/agi.py b/asterisk/agi.py
index 8065cde..72f94da 100644
--- a/asterisk/agi.py
+++ b/asterisk/agi.py
@@ -113,7 +113,7 @@ class AGI:
         sys.stderr.write('\n')
 
     def _quote(self, string):
-        return ''.join(['"', str(string), '"'])
+        return ''.join(['"', string.encode('ascii', 'ignore'), '"'])
 
     def _handle_sighup(self, signum, frame):
         """Handle the SIGHUP signal"""