Index: channels/chan_zap.c
===================================================================
--- channels/chan_zap.c	(revision 120060)
+++ channels/chan_zap.c	(working copy)
@@ -6242,7 +6242,10 @@
 							ast_hangup(chan);
 							return NULL;
 						} 
-						f = ast_read(chan);
+						if (!(f = ast_read(chan))) {
+							ast_hangup(chan);
+							return NULL;
+						}
 						ast_frfree(f);
 						if (chan->_state == AST_STATE_RING ||
 						    chan->_state == AST_STATE_RINGING)