Systems, apparatuses, and methods related to modified checksum data using a poison data indictor. An example method can include receiving a first set of bits including data and a second set of at least one bit indicating whether the first set of bits includes one or more erroneous or corrupted bits. A first checksum can be generated that is associated with the first set of bits. A second checksum can be generated using the first checksum and the second set of at least one bit. The first set of bits and the second checksum can be written to an array of a memory device. A comparison of the first checksum and the second checksum can indicate whether the first set of bits includes the at least one or more erroneous or corrupted bits.