Change of behaviour of OR in IF-conditions 10.2 -> 10.3

The behavior of the OR operator in the IF condition has changed from MariaDB 10.2 to 10.3.
now I noticed that the following syntax doesn't work in SELECT statements anymore:

SELECT * FROM tab t WHERE IF(@a = 1, t.a = 1 OR t.b = 1,1=1)

Now I'd have to write:

SELECT * FROM tab t WHERE (IF(@a = 1, t.a = 1, 1=1) OR IF(@a = 1, t.b = 1, 1=1))

Is it a bug or a deliberate change? Is there a setting with which I can reactivate the previous behavior?