Small river full house facing minraise

[sublyme]

Live loose cash home game, 7 handed $0.25/$0.50 blinds with max 20 buyin, but there were plenty of rebuys/reloads so stacks were fairly deep. I have roughly $50. All limp to me in the BB and I check with 44. Flop rolls Ah 5x Kc. Check all around. Turn is Ac. Check all around. River is 4c. SB check, then I bet $4. Guy behind me minraises another $4. Fold back to me. This is an insta-raise, right?