Issue on GRANT query

[ldragone]

I'm having trouble running grant queries.

The variables are:
tableArray = ['schema.table1','schema.table2']
roleName = 'example'

This query works fine:
GRANT INSERT ON ${this.sql(tableArray)} TO ${this.sql(roleName)}

the generated query is correct:
GRANT SELECT ON "schema"."table1","schema"."table2" TO "example"

This one doesn't work:
GRANT UPDATE ON ${this.sql(tableArray)} TO ${this.sql(roleName)}

the generated query is invalid:
GRANT UPDATE ON "0"=$1,"1"=$2 TO "example"

Is this a bug in the system that understands what to replace in the query?