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# TxEnvelopeEip1559.assert

:::info
`TxEnvelopeEip1559.assert` is a re-export of ox's [`TxEnvelopeEip1559.assert`](https://oxlib.sh/api/TxEnvelopeEip1559/assert). Refer to the ox documentation for the full reference.
:::

Asserts a [`TxEnvelopeEip1559.TxEnvelopeEip1559`](/docs/utilities/txenvelopeeip1559/types#txenvelopeeip1559) is valid.

## Imports

```ts
import { TxEnvelopeEip1559 } from 'viem/utils'
```

## Examples

```ts twoslash
// @noErrors
import { TxEnvelopeEip1559, Value } from 'viem/utils'

TxEnvelopeEip1559.assert({
  maxFeePerGas: 2n ** 256n - 1n + 1n,
  chainId: 1,
  to: '0x0000000000000000000000000000000000000000',
  value: Value.fromEther('1')
})
// @error: FeeCapTooHighError:
// @error: The fee cap (`masFeePerGas` = 115792089237316195423570985008687907853269984665640564039457584007913 gwei) cannot be
// @error: higher than the maximum allowed value (2^256-1).
```

## Definition

```ts
function assert(
  envelope: PartialBy<TxEnvelopeEip1559, 'type'>,
): void
```

## Parameters

### envelope

* **Type:** `PartialBy<TxEnvelopeEip1559, 'type'>`

The transaction envelope to assert.

## Return Type

`void`