Ethereum Classic activated the Mystique network upgrade at block 14,525,000 on February 12, 2022. Mystique adopted a subset of Ethereum's London hard fork changes, specified in ECIP-1104.
Included EIPs
- EIP-3529 — Alternative Refund Reduction: Eliminated SELFDESTRUCT refund (24,000 → 0 gas) and capped SSTORE refunds at 20% of transaction gas. This change made gas token contracts (CHI, GST2) economically unviable, removing a long-standing abuse vector that complicated gas estimation.
- EIP-3541 — Reject New Contracts Starting with 0xEF: New contract deployments with bytecode starting at 0xEF are rejected. Existing contracts are unaffected. This reserves the 0xEF prefix for the future EVM Object Format (EOF), preventing bytecode collisions.
Omitted EIPs
- EIP-1559 (Fee Market Change): EIP-1559 burns the transaction basefee, permanently destroying tokens. This conflicts with ETC's fixed monetary policy under ECIP-1017 (~210.7M cap). The community chose to defer EIP-1559 adoption — the Olympia network upgrade redirects the basefee to a community treasury (ECIP-1112) instead of burning it, preserving the monetary policy while adopting the fee market mechanism.
- EIP-3198 (BASEFEE Opcode): Depends on EIP-1559; without an active basefee, the opcode has no defined return value.
- EIP-3228 (Difficulty Bomb Delay): ETC permanently removed the difficulty bomb in ECIP-1041 (block 5,900,000). Not applicable.
Client Requirements
- Core-Geth v1.12.9 or later
- Hyperledger Besu with ETC Mystique support