"Missing comma before start of a new alter operation. (near COALESCE)" for valid statement

[bmcn99]

The following command:

ALTER TABLE orders 
ADD COLUMN `n_deleted_at` timestamp AS (COALESCE(deleted_at, '1980-01-01')) VIRTUAL;

Produces the sql-parser error "Missing comma before start of a new alter operation. (near COALESCE)". The command still goes through just fine though.

This is on version phpmyadmin 4.9.5 and 4.9.5deb2.