# AA50 postOp reverted

`AA50 postOp reverted` is an ERC-4337 EntryPoint error that means the paymaster's `postOp` function reverted after the user operation was executed.

:::info
`postOp` is a function that is called by the EntryPoint on the paymaster contract after the user operation execution is completed. It is often used by paymasters to perform additional accounting logic.
:::

The paymaster contract's `postOp` function reverted.

## Possible solutions

* If you are using your own paymaster contract, verify that that you have correctly implemented the `postOp` function (if you are using one). If you do *not* intent to make use of the `postOp` function, make sure you do not set the `context` parameter in the paymaster's `validatePaymasterUserOp` function.
* If you are using a paymaster service like Pimlico and you see this error, [reach out to them](https://t.me/pimlicoHQ).
* If all else fails, investigate why the `postOp` function reverted using tools like [Tenderly](https://tenderly.co/).