Index: main/channel.c
===================================================================
--- main/channel.c	(revision 407165)
+++ main/channel.c	(working copy)
@@ -7087,8 +7087,9 @@
 
 	/* Copy the FD's other than the generator fd */
 	for (x = 0; x < AST_MAX_FDS; x++) {
-		if (x != AST_GENERATOR_FD)
+		if (x != AST_GENERATOR_FD && ast_channel_fd_isset(clonechan, x)) {
 			ast_channel_set_fd(original, x, ast_channel_fd(clonechan, x));
+		}
 	}
 
 	ast_app_group_update(clonechan, original);