---
title: Troubleshoot hyperfunctions | Tiger Data Docs
description: Solutions to common errors with hyperfunctions and TimescaleDB Toolkit
---

## Queries using `locf()` don’t treat NULL values as missing

When you have a query that uses a last observation carried forward (locf) function, the query carries forward NULL values by default. If you want the function to ignore NULL values instead, you can set `treat_null_as_missing=TRUE` as the second parameter in the query. For example:

```
dev=# select * FROM (select time_bucket_gapfill(4, time,-5,13), locf(avg(v)::int,treat_null_as_missing:=true) FROM (VALUES (0,0),(8,NULL)) v(time, v) WHERE time BETWEEN 0 AND 10 GROUP BY 1) i ORDER BY 1 DESC;
 time_bucket_gapfill | locf
---------------------+------
                  12 |    0
                   8 |    0
                   4 |    0
                   0 |    0
                  -4 |
                  -8 |
(6 rows)
```