--- asterisk-1.8.15.0.o/main/pbx.c	2012-07-10 15:33:53.000000000 +0200
+++ asterisk-1.8.15.0/main/pbx.c	2012-10-30 17:21:11.793027046 +0200
@@ -6878,23 +6878,26 @@
 
 	manager_show_dialplan_helper(s, m, idtext, context, exten, &counters, NULL);
 
-	if (context && !counters.context_existence) {
+	if (!ast_strlen_zero(context) && !counters.context_existence) {
 		char errorbuf[BUFSIZ];
 
 		snprintf(errorbuf, sizeof(errorbuf), "Did not find context %s", context);
 		astman_send_error(s, m, errorbuf);
 		return 0;
 	}
-	if (exten && !counters.extension_existence) {
+	if (!ast_strlen_zero(exten) && !counters.extension_existence) {
 		char errorbuf[BUFSIZ];
 
-		if (context)
+		if (!ast_strlen_zero(context))
 			snprintf(errorbuf, sizeof(errorbuf), "Did not find extension %s@%s", exten, context);
 		else
 			snprintf(errorbuf, sizeof(errorbuf), "Did not find extension %s in any context", exten);
 		astman_send_error(s, m, errorbuf);
 		return 0;
 	}
+	if (counters.total_items == 0) {
+		manager_dpsendack(s, m);
+	}
 
 	astman_append(s, "Event: ShowDialPlanComplete\r\n"
 		"EventList: Complete\r\n"