DHCP stops working the morning after DHCP snooping was enabled

Last night a security change enabled DHCP snooping for VLAN 40 on access switch ASW1, with the uplink Gi1/0/48 to R1 marked as trusted. This morning, laptops that need a new lease (new arrivals, or leases that ran out overnight) get 169.254.x.x addresses. Users whose lease is still valid work normally. R1 is both the gateway (Gi0/0/1.40, 10.40.0.1/24) and the DHCP server for VLAN 40, with a local pool. There is no relay in the path.