Problem with "NULL" type when using "COUNT(id)"

[msrd0]

I have this query:

pub struct Stat {
	offering: String,
	count: u32
}

sqlx::query_as!(
    Stat,
    r#"
	    SELECT offerings.readable_name AS offering, COUNT(transactions.id) AS 'count!'
	    FROM transactions
	    INNER JOIN offerings ON offering_id = offerings.name
	    WHERE timestamp BETWEEN ?1 AND ?2
	    GROUP BY offering_id;
    "#,
    start,
    end
)

This fails to compile:

error: unsupported type NULL of column #2 ("count!")
  --> src/sql/stats.rs:16:2
   |
16 | /     sqlx::query_as!(
17 | |         Stat,
18 | |         r#"
19 | |             SELECT offerings.readable_name AS offering, COUNT(transactions.id) AS 'count!'
...  |
26 | |         end
27 | |     )
   | |_____^
   |
   = note: this error originates in the macro `$crate::sqlx_macros::expand_query` which comes from the expansion of the macro `sqlx::query_as` (in Nightly builds, run with -Z macro-backtrace for more info)

Why does this fail and how can I fix this?