diff --git a/src/parser_json.c b/src/parser_json.c
index 17bc38b565ae..8d5aa480ae04 100644
--- a/src/parser_json.c
+++ b/src/parser_json.c
@@ -3395,6 +3395,14 @@ static struct cmd *json_parse_cmd_add_set(struct json_ctx *ctx, json_t *root,
 		return NULL;
 	}
 
+	if (set->key->etype == EXPR_CONCAT &&
+	    list_empty(&set->key->expressions)) {
+		json_error(ctx, "Empty set type.");
+		set_free(set);
+		handle_free(&h);
+		return NULL;
+	}
+
 	if (!json_unpack(root, "{s:o}", "map", &tmp)) {
 		if (json_is_string(tmp)) {
 			const char *s = json_string_value(tmp);