diff --git a/ethereum/contracts/bridge/BridgeImplementation.sol b/ethereum/contracts/bridge/BridgeImplementation.sol
index 4365e7a51..ccc6f34b3 100644
--- a/ethereum/contracts/bridge/BridgeImplementation.sol
+++ b/ethereum/contracts/bridge/BridgeImplementation.sol
@@ -18,43 +18,26 @@ contract BridgeImplementation is Bridge {
     function initialize() initializer public virtual {
         // this function needs to be exposed for an upgrade to pass
         address tokenContract;
-        uint256 evmChainId;
-        uint16 chain = chainId();
+        uint256 chain = chainId();
 
-        // Wormhole chain ids explicitly enumerated
-        if        (chain == 2)  { evmChainId = 1;          // ethereum
-            setFinality(1);
-            tokenContract = 0x0fD04a68d3c3A692d6Fa30384D1A87Ef93554eE6;
-        } else if (chain == 4)  { evmChainId = 56;         // bsc
-            tokenContract = 0x7f8C5e730121657E17E452c5a1bA3fA1eF96f22a;
-        } else if (chain == 5)  { evmChainId = 137;        // polygon
-            tokenContract = 0x7C9Fc5741288cDFdD83CeB07f3ea7e22618D79D2;
-        } else if (chain == 6)  { evmChainId = 43114;      // avalanche
-            tokenContract = 0xe07548528D7c0C470251CF1374eF762345f298eE;
-        } else if (chain == 7)  { evmChainId = 42262;      // oasis
-            tokenContract = 0x75d520ed7fE263b96cCC7165aCe270097bC11721;
-        } else if (chain == 9)  { evmChainId = 1313161554; // aurora
-            tokenContract = 0x20F989Ad4C3B6ddcd940A66013d45f45d5c15463;
-        } else if (chain == 10) { evmChainId = 250;        // fantom
-            tokenContract = 0x99A3385C5AA40B184F6F6898daeBcD752C4b11F8;
-        } else if (chain == 11) { evmChainId = 686;        // karura
-            tokenContract = 0x7C9Fc5741288cDFdD83CeB07f3ea7e22618D79D2;
-        } else if (chain == 12) { evmChainId = 787;        // acala
-        } else if (chain == 13) { evmChainId = 8217;       // klaytn
-            tokenContract = 0x7Ec2f3742F5D7ecF85817D67Ae3f89fa70164e8F;
-        } else if (chain == 14) { evmChainId = 42220;      // celo
-            tokenContract = 0x1a81c975d0e69206a45584BB98520f25dEEC7b6C;
-        } else if (chain == 16) { evmChainId = 1284;       // moonbeam
-            tokenContract = 0xddA94dA500AF7DCd8DE53482a39eD55d4aA3B392;
-        } else if (chain == 17) { evmChainId = 245022934;  // neon
-        } else if (chain == 23) { evmChainId = 42161;      // arbitrum
-        } else if (chain == 24) { evmChainId = 10;         // optimism
-        } else if (chain == 25) { evmChainId = 100;        // gnosis
+        // A previous upgrade
+        // (https://github.com/wormhole-foundation/wormhole/commit/cb161db5e01970cc92d80fc679e506db054f8368)
+        // set the token contract implementations for a number of chains,
+        // excluding arbitrum and optimism, both of which were deployed with
+        // that `initialize` contract, meaning there's a potential for a
+        // temporary DoS.
+        //
+        // Performing this upgrade closes that DoS window.
+        //
+        // *insert rant about implicit variable initialisation*
+        if        (chain == 23) { // arbitrum
+            tokenContract = 0x53B56de645B9de6e5a40acE047D1c74E8B42Eccb;
+        } else if (chain == 24) { // optimism
+            tokenContract = 0xb91e3638F82A1fACb28690b37e3aAE45d2c33808;
         } else {
-            revert("Unknown chain id.");
+            revert("Chain not handled.");
         }
 
-        setEvmChainId(evmChainId);
         setTokenImplementation(tokenContract);
     }