diff --git a/build/scripts/testing.mk b/build/scripts/testing.mk
index 5ad602d88d..c48efd7ba3 100644
--- a/build/scripts/testing.mk
+++ b/build/scripts/testing.mk
@@ -118,7 +118,7 @@ start-erigon: ## start an ephemeral `erigon` node
 	--authrpc.addr	0.0.0.0 \
 	--authrpc.jwtsecret $(JWT_PATH) \
 	--authrpc.vhosts "*" \
-	--networkid 80087 \
+	--networkid 80086 \
 	--db.size.limit	3000MB \
 	--datadir .tmp/erigon
 
diff --git a/kurtosis/kurtosis-params.yaml b/kurtosis/kurtosis-params.yaml
index f877b46d33..f961ae0ead 100644
--- a/kurtosis/kurtosis-params.yaml
+++ b/kurtosis/kurtosis-params.yaml
@@ -25,4 +25,4 @@
 
 network_params:
   network_name: "kurtosis"
-  network_id: "80087"
\ No newline at end of file
+  network_id: "80086"
\ No newline at end of file
diff --git a/kurtosis/src/networks/kurtosis-devnet/network-configs/genesis.json b/kurtosis/src/networks/kurtosis-devnet/network-configs/genesis.json
index 3ae56b273a..148136f267 100644
--- a/kurtosis/src/networks/kurtosis-devnet/network-configs/genesis.json
+++ b/kurtosis/src/networks/kurtosis-devnet/network-configs/genesis.json
@@ -1,6 +1,6 @@
 {
   "config": {
-    "chainId": 80087,
+    "chainId": 80086,
     "homesteadBlock": 0,
     "daoForkBlock": 0,
     "daoForkSupport": true,
diff --git a/kurtosis/src/nodes/consensus/beacond/launcher.star b/kurtosis/src/nodes/consensus/beacond/launcher.star
index c452ea9ca4..70adeddf60 100644
--- a/kurtosis/src/nodes/consensus/beacond/launcher.star
+++ b/kurtosis/src/nodes/consensus/beacond/launcher.star
@@ -48,12 +48,12 @@ def get_config(image, engine_dial_url, cl_service_name, entrypoint = [], cmd = [
             "BEACOND_MONIKER": cl_service_name,
             "BEACOND_NET": "VALUE_2",
             "BEACOND_HOME": "/root/.beacond",
-            "BEACOND_CHAIN_ID": "beacon-kurtosis-80087",
+            "BEACOND_CHAIN_ID": "beacon-kurtosis-80086",
             "BEACOND_DEBUG": "false",
             "BEACOND_KEYRING_BACKEND": "test",
             "BEACOND_MINIMUM_GAS_PRICE": "0abgt",
             "BEACOND_ENGINE_DIAL_URL": engine_dial_url,
-            "BEACOND_ETH_CHAIN_ID": "80087",
+            "BEACOND_ETH_CHAIN_ID": "80086",
             "BEACOND_PERSISTENT_PEERS": persistent_peers,
             "BEACOND_ENABLE_PROMETHEUS": "true",
             "BEACOND_CONSENSUS_KEY_ALGO": "bls12_381",
diff --git a/kurtosis/src/nodes/consensus/beacond/node.star b/kurtosis/src/nodes/consensus/beacond/node.star
index 2fbb499134..7e469a2146 100644
--- a/kurtosis/src/nodes/consensus/beacond/node.star
+++ b/kurtosis/src/nodes/consensus/beacond/node.star
@@ -65,11 +65,11 @@ def get_genesis_env_vars(cl_service_name):
         "BEACOND_MONIKER": cl_service_name,
         "BEACOND_NET": "VALUE_2",
         "BEACOND_HOME": "/root/.beacond",
-        "BEACOND_CHAIN_ID": "beacon-kurtosis-80087",
+        "BEACOND_CHAIN_ID": "beacon-kurtosis-80086",
         "BEACOND_DEBUG": "false",
         "BEACOND_KEYRING_BACKEND": "test",
         "BEACOND_MINIMUM_GAS_PRICE": "0abgt",
-        "BEACOND_ETH_CHAIN_ID": "80087",
+        "BEACOND_ETH_CHAIN_ID": "80086",
         "BEACOND_ENABLE_PROMETHEUS": "true",
         "BEACOND_CONSENSUS_KEY_ALGO": "bls12_381",
         "ETH_GENESIS": "/root/eth_genesis/genesis.json",
diff --git a/kurtosis/src/nodes/execution/erigon/config.star b/kurtosis/src/nodes/execution/erigon/config.star
index 07696d5426..9afefd409e 100644
--- a/kurtosis/src/nodes/execution/erigon/config.star
+++ b/kurtosis/src/nodes/execution/erigon/config.star
@@ -89,7 +89,7 @@ CMD = [
     "--metrics.port",
     "{}".format(METRICS_PORT_NUM),
     "--networkid",
-    "80087",
+    "80086",
     "--db.size.limit={}MB".format(3000),
 ]
 BOOTNODE_CMD = "--bootnodes"
diff --git a/kurtosis/src/nodes/execution/geth/config.star b/kurtosis/src/nodes/execution/geth/config.star
index 15cb633017..565ff46114 100644
--- a/kurtosis/src/nodes/execution/geth/config.star
+++ b/kurtosis/src/nodes/execution/geth/config.star
@@ -60,7 +60,7 @@ CMD = [
     "--datadir",
     EXECUTION_DATA_DIRPATH_ON_CLIENT_CONTAINER,
     "--networkid",
-    "80087",
+    "80086",
 ]
 BOOTNODE_CMD = "--bootnodes"
 
diff --git a/kurtosis/src/nodes/execution/geth/geth-config.toml b/kurtosis/src/nodes/execution/geth/geth-config.toml
index 8c5d64310b..228c11d623 100644
--- a/kurtosis/src/nodes/execution/geth/geth-config.toml
+++ b/kurtosis/src/nodes/execution/geth/geth-config.toml
@@ -1,5 +1,5 @@
 [Eth]
-NetworkId = 80087
+NetworkId = 80086
 SyncMode = "full"
 EthDiscoveryURLs = []
 SnapDiscoveryURLs = []
diff --git a/mod/node-builder/pkg/config/spec/localnet.go b/mod/node-builder/pkg/config/spec/localnet.go
index d859a99931..1e924000b3 100644
--- a/mod/node-builder/pkg/config/spec/localnet.go
+++ b/mod/node-builder/pkg/config/spec/localnet.go
@@ -47,7 +47,7 @@ func LocalnetChainSpec() chain.Spec[
 			common.ExecutionAddress,
 			math.Slot,
 		]{
-			Eth1ChainID: uint64(80087),
+			Eth1ChainID: uint64(80086),
 			// // Gwei value constants.
 			MinDepositAmount:          uint64(1e9),
 			MaxEffectiveBalance:       uint64(32e9),
diff --git a/testing/files/eth-genesis.json b/testing/files/eth-genesis.json
index 5124f72553..844508f01c 100644
--- a/testing/files/eth-genesis.json
+++ b/testing/files/eth-genesis.json
@@ -1,6 +1,6 @@
 {
   "config": {
-    "chainId": 80087,
+    "chainId": 80086,
     "homesteadBlock": 0,
     "daoForkBlock": 0,
     "daoForkSupport": true,