Some partnerships prefer to interchange the meanings of the 4 and 4 bids following a 3 preempt so that 4 denotes diamonds and an undisclosed major.
In bridge bidding, some partnerships alter their bidding system following a 3 preempt by swapping the meaning of bids 4 and 4. This change signifies that bid 4 now indicates diamonds, while bid 4 still represents an undisclosed major.