diff --git a/daemon/call_interfaces.c b/daemon/call_interfaces.c
index 26fe6e7fd..299a060c5 100644
--- a/daemon/call_interfaces.c
+++ b/daemon/call_interfaces.c
@@ -2742,7 +2742,7 @@ stats:
 	}
 }
 
-static void ng_list_calls(bencode_item_t *output, long long int limit) {
+static void ng_list_calls(ng_parser_ctx_t *ctx, bencode_item_t *output, long long int limit) {
 	rtpe_calls_ht_iter iter;
 
 	rwlock_lock_r(&rtpe_callhash_lock);
@@ -2750,7 +2750,7 @@ static void ng_list_calls(bencode_item_t *output, long long int limit) {
 	t_hash_table_iter_init (&iter, rtpe_callhash);
 	str *key;
 	while (limit-- && t_hash_table_iter_next (&iter, &key, NULL)) {
-		bencode_list_add_str_dup(output, key);
+		ctx->parser->list_add_str_dup(output, key);
 	}
 
 	rwlock_unlock_r(&rtpe_callhash_lock);
@@ -2792,7 +2792,7 @@ const char *call_list_ng(ng_parser_ctx_t *ctx) {
 	}
 	calls = ctx->parser->dict_add_list(output, "calls");
 
-	ng_list_calls(calls, limit);
+	ng_list_calls(ctx, calls, limit);
 
 	return NULL;
 }
diff --git a/daemon/control_ng.c b/daemon/control_ng.c
index 1d8b656fc..adbc09d41 100644
--- a/daemon/control_ng.c
+++ b/daemon/control_ng.c
@@ -346,6 +346,7 @@ const ng_parser_t ng_parser_native = {
 	.list_add = bencode_list_add,
 	.list_add_dict = bencode_list_add_dictionary,
 	.list_add_string = bencode_list_add_string,
+	.list_add_str_dup = bencode_list_add_str_dup,
 	.pretty_print = bencode_pretty_print,
 };
 const ng_parser_t ng_parser_json = {
@@ -375,6 +376,7 @@ const ng_parser_t ng_parser_json = {
 	.list_add = bencode_list_add,
 	.list_add_dict = bencode_list_add_dictionary,
 	.list_add_string = bencode_list_add_string,
+	.list_add_str_dup = bencode_list_add_str_dup,
 	.pretty_print = json_pretty_print,
 };
 
diff --git a/include/control_ng.h b/include/control_ng.h
index da353cf7e..c08932bc8 100644
--- a/include/control_ng.h
+++ b/include/control_ng.h
@@ -144,6 +144,7 @@ struct ng_parser {
 	parser_arg (*list)(ng_parser_ctx_t *);
 	bencode_item_t *(*list_add)(parser_arg, parser_arg);
 	bencode_item_t *(*list_add_dict)(bencode_item_t *);
+	void (*list_add_str_dup)(parser_arg, const str *);
 	void (*list_add_string)(bencode_item_t *, const char *);
 	void (*pretty_print)(parser_arg, GString *);
 };