--- main/pbx_app.c.orig	2016-11-23 16:26:01.000000000 +0100
+++ main/pbx_app.c	2017-06-08 11:03:28.909551100 +0200
@@ -397,6 +397,11 @@
 	struct ast_app *cur;
 	int cmp;
 
+	/* Anticipate need for conlock in unreference_cached_app(), in order to avoid
+	 * possible deadlock with pbx_extension_helper()/pbx_findapp()
+	 */
+	ast_rdlock_contexts();
+
 	AST_RWLIST_WRLOCK(&apps);
 	AST_RWLIST_TRAVERSE_SAFE_BEGIN(&apps, cur, list) {
 		cmp = strcasecmp(app, cur->name);
@@ -419,6 +424,8 @@
 	AST_RWLIST_TRAVERSE_SAFE_END;
 	AST_RWLIST_UNLOCK(&apps);
 
+	ast_unlock_contexts();
+
 	return cur ? 0 : -1;
 }