diff --git a/src/Nethermind/Chains/base-mainnet.json b/src/Nethermind/Chains/base-mainnet.json
index 642f5ae56c0..eb4c84a03b7 100644
--- a/src/Nethermind/Chains/base-mainnet.json
+++ b/src/Nethermind/Chains/base-mainnet.json
@@ -10,6 +10,7 @@
         "ecotoneTimestamp": "0x65f23e01",
         "fjordTimestamp": "0x668eb001",
         "graniteTimestamp": "0x66e1be81",
+        "holoceneTimestamp": "0x67800ea1",
         "l1FeeRecipient": "0x420000000000000000000000000000000000001A",
         "l1BlockAddress": "0x4200000000000000000000000000000000000015",
         "canyonBaseFeeChangeDenominator": "250",
@@ -71,6 +72,7 @@
 
     "rip7212TransitionTimestamp": "0x668eb001",
     "opGraniteTransitionTimestamp": "0x66e1be81",
+    "opHoloceneTransitionTimestamp": "0x67800ea1",
 
     "terminalTotalDifficulty": "0"
   },
diff --git a/src/Nethermind/Chains/op-mainnet.json b/src/Nethermind/Chains/op-mainnet.json
index 92b65c15058..ac66f64183d 100644
--- a/src/Nethermind/Chains/op-mainnet.json
+++ b/src/Nethermind/Chains/op-mainnet.json
@@ -10,6 +10,7 @@
         "ecotoneTimestamp": "0x65f23e01",
         "fjordTimestamp": "0x668eb001",
         "graniteTimestamp": "0x66e1be81",
+        "holoceneTimestamp": "0x67800ea1",
         "l1FeeRecipient": "0x420000000000000000000000000000000000001A",
         "l1BlockAddress": "0x4200000000000000000000000000000000000015",
         "canyonBaseFeeChangeDenominator": "250",
@@ -76,6 +77,7 @@
 
     "rip7212TransitionTimestamp": "0x668eb001",
     "opGraniteTransitionTimestamp": "0x66e1be81",
+    "opHoloceneTransitionTimestamp": "0x67800ea1",
 
     "terminalTotalDifficulty": "210470125"
   },