Error $2eb9, update on primary key of master table

Using BDE 5.10 with 11/19/99 Local SQL driver update.

Two Paradox tables linked with referential integrity, with cascade
updates. Primary key of master is Alpha field ("Name") and the RI link
is on this field. Trying to execute the following Local SQL query:

  UPDATE "MyMaster.db" M
  SET M."Name" = UPPER(M."Name")

generates BDE error $2eb9, "Update on Primary Key of a Master Table may
modify more than one record."

It looks to me like this query SHOULD work. The new key value should
cascade to the detail tables. Is this a known bug? Is there a