> ## Documentation Index
> Fetch the complete documentation index at: https://starkware-9575960b-chore-starknet-docs-url-migration.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# core::starknet::syscalls::replace_class_syscall

Replaces the class hash of the current contract, instantly modifying its entrypoints.
The new class becomes effective only after the current function call completes.
The remaining code in the current function will continue executing from the old class.
The new class will be used:

* In subsequent transactions
* If the contract is called via `call_contract` syscall later in the same transaction

## Signature

```rust theme={null}
pub extern fn replace_class_syscall(class_hash: ClassHash) -> Result> implicits(GasBuiltin, System) nopanic;
```

#### Arguments

* `class_hash` - The class hash that should replace the current one.