diff --git a/daemon/call_interfaces.c b/daemon/call_interfaces.c
index 9aa33fe59..af2f678a0 100644
--- a/daemon/call_interfaces.c
+++ b/daemon/call_interfaces.c
@@ -690,17 +690,17 @@ INLINE void ng_sdp_attr_manipulations(ng_parser_ctx_t *ctx, bencode_item_t *valu
 			switch (__csh_lookup(&command_type)) {
 
 				case CSH_LOOKUP("substitute"):
-					call_ng_flags_list(NULL, command_value, call_ng_flags_str_pair_ht, call_ng_flags_item_pair_ht,
+					call_ng_flags_list(ctx, command_value, call_ng_flags_str_pair_ht, call_ng_flags_item_pair_ht,
 							&sm->subst_commands);
 					break;
 
 				case CSH_LOOKUP("add"):
-					call_ng_flags_str_list(NULL, command_value, call_ng_flags_esc_str_list, &sm->add_commands);
+					call_ng_flags_str_list(ctx, command_value, call_ng_flags_esc_str_list, &sm->add_commands);
 					break;
 
 				/* CMD_REM commands */
 				case CSH_LOOKUP("remove"):
-					call_ng_flags_str_list(NULL, command_value, call_ng_flags_str_ht, &sm->rem_commands);
+					call_ng_flags_str_list(ctx, command_value, call_ng_flags_str_ht, &sm->rem_commands);
 					break;
 
 				default:
@@ -795,9 +795,10 @@ static void call_ng_flags_list(ng_parser_ctx_t *ctx, bencode_item_t *list,
 		void (*item_callback)(ng_parser_ctx_t *, bencode_item_t *, helper_arg),
 		helper_arg arg)
 {
+	const ng_parser_t *parser = ctx->parser;
 	str s;
-	if (list->type != BENCODE_LIST) {
-		if (bencode_get_str(list, &s)) {
+	if (!parser->is_list(list)) {
+		if (parser->get_str(list, &s)) {
 			str token;
 			while (str_token_sep(&token, &s, ','))
 				str_callback(ctx, &token, arg);
@@ -806,14 +807,7 @@ static void call_ng_flags_list(ng_parser_ctx_t *ctx, bencode_item_t *list,
 			ilog(LOG_DEBUG, "Ignoring non-list non-string value");
 		return;
 	}
-	for (bencode_item_t *it = list->child; it; it = it->sibling) {
-		if (bencode_get_str(it, &s))
-			str_callback(ctx, &s, arg);
-		else if (item_callback)
-			item_callback(ctx, it, arg);
-		else
-			ilog(LOG_DEBUG, "Ignoring non-string value in list");
-	}
+	parser->list_iter(ctx, list, str_callback, item_callback, arg);
 }
 static void call_ng_flags_str_list(ng_parser_ctx_t *ctx, bencode_item_t *list,
 		void (*callback)(ng_parser_ctx_t *ctx, str *, helper_arg), helper_arg arg)
diff --git a/daemon/control_ng.c b/daemon/control_ng.c
index 3ec160434..8ae15c2a1 100644
--- a/daemon/control_ng.c
+++ b/daemon/control_ng.c
@@ -98,16 +98,40 @@ static void bencode_dict_iter(ng_parser_ctx_t *ctx, bencode_item_t *input,
 		callback(ctx, &k, value);
 	}
 }
+static bool bencode_is_list(bencode_item_t *arg) {
+	return arg->type == BENCODE_LIST;
+}
+static void bencode_list_iter(ng_parser_ctx_t *ctx, bencode_item_t *list,
+		void (*str_callback)(ng_parser_ctx_t *, str *key, helper_arg),
+		void (*item_callback)(ng_parser_ctx_t *, bencode_item_t *, helper_arg),
+		helper_arg arg)
+{
+	if (list->type != BENCODE_LIST)
+		return;
+	str s;
+	for (bencode_item_t *it = list->child; it; it = it->sibling) {
+		if (bencode_get_str(it, &s))
+			str_callback(ctx, &s, arg);
+		else if (item_callback)
+			item_callback(ctx, it, arg);
+		else
+			ilog(LOG_DEBUG, "Ignoring non-string value in list");
+	}
+}
 
 const ng_parser_t ng_parser_native = {
 	.collapse = bencode_collapse_str,
 	.dict_iter = bencode_dict_iter,
+	.is_list = bencode_is_list,
+	.list_iter = bencode_list_iter,
 	.get_str = bencode_get_str,
 	.get_int_str = bencode_get_integer_str,
 };
 const ng_parser_t ng_parser_json = {
 	.collapse = bencode_collapse_str_json,
 	.dict_iter = bencode_dict_iter,
+	.is_list = bencode_is_list,
+	.list_iter = bencode_list_iter,
 	.get_str = bencode_get_str,
 	.get_int_str = bencode_get_integer_str,
 };
diff --git a/daemon/statistics.c b/daemon/statistics.c
index 809e7b412..e48d432c6 100644
--- a/daemon/statistics.c
+++ b/daemon/statistics.c
@@ -1007,7 +1007,7 @@ const char *statistics_ng(ng_parser_ctx_t *ctx) {
 			assert(sub_label != NULL);
 			bencode_dictionary_add(dict, bencode_strdup(buf, sub_label), sub);
 		}
-		else if (dict->type == BENCODE_LIST)
+		else if (ctx->parser->is_list(dict))
 			bencode_list_add(dict, sub);
 		else
 			abort();
diff --git a/include/call_interfaces.h b/include/call_interfaces.h
index 4b132b9c5..c15c7854a 100644
--- a/include/call_interfaces.h
+++ b/include/call_interfaces.h
@@ -14,14 +14,6 @@ struct call_stats;
 struct streambuf_stream;
 struct sockaddr_in6;
 
-typedef union {
-	const struct sdp_attr_helper *attr_helper;
-	str_q *q;
-	str_case_ht *sct;
-	str_case_value_ht *svt;
-	void **generic;
-} helper_arg  __attribute__ ((__transparent_union__));
-
 struct sdp_ng_flags {
 	enum call_opmode opmode;
 	enum message_type message_type;
diff --git a/include/control_ng.h b/include/control_ng.h
index 7a2078298..12f19401b 100644
--- a/include/control_ng.h
+++ b/include/control_ng.h
@@ -97,10 +97,23 @@ enum call_opmode {
 	OP_OTHER,
 };
 
+typedef union {
+	const struct sdp_attr_helper *attr_helper;
+	str_q *q;
+	str_case_ht *sct;
+	str_case_value_ht *svt;
+	void *generic;
+} helper_arg  __attribute__ ((__transparent_union__));
+
 struct ng_parser {
 	str *(*collapse)(bencode_item_t *root, str *out);
 	void (*dict_iter)(ng_parser_ctx_t *, bencode_item_t *,
 		void (*callback)(ng_parser_ctx_t *, str *, bencode_item_t *));
+	bool (*is_list)(bencode_item_t *);
+	void (*list_iter)(ng_parser_ctx_t *, bencode_item_t *input,
+			void (*str_callback)(ng_parser_ctx_t *, str *key, helper_arg),
+			void (*item_callback)(ng_parser_ctx_t *, bencode_item_t *, helper_arg),
+			helper_arg);
 	str *(*get_str)(bencode_item_t *, str *s);
 	long long (*get_int_str)(bencode_item_t *, long long def);
 };