diff --git a/crates/optimism/chainspec/src/lib.rs b/crates/optimism/chainspec/src/lib.rs
index e8f8a084e..2735b77dd 100644
--- a/crates/optimism/chainspec/src/lib.rs
+++ b/crates/optimism/chainspec/src/lib.rs
@@ -190,6 +190,11 @@ pub struct OpChainSpec {
 }
 
 impl OpChainSpec {
+    /// Converts the given [`Genesis`] into a [`OpChainSpec`].
+    pub fn from_genesis(genesis: Genesis) -> Self {
+        genesis.into()
+    }
+
     /// Extracts the Holocene 1599 parameters from the encoded extra data from the parent header.
     ///
     /// Caution: Caller must ensure that holocene is active in the parent header.
@@ -1112,4 +1117,63 @@ mod tests {
         let base_fee = op_chain_spec.next_block_base_fee(&parent, 1735315546).unwrap();
         assert_eq!(base_fee, U256::from(507));
     }
+
+    #[test]
+    fn json_genesis() {
+        let geth_genesis = r#"
+{
+    "config": {
+        "chainId": 1301,
+        "homesteadBlock": 0,
+        "eip150Block": 0,
+        "eip155Block": 0,
+        "eip158Block": 0,
+        "byzantiumBlock": 0,
+        "constantinopleBlock": 0,
+        "petersburgBlock": 0,
+        "istanbulBlock": 0,
+        "muirGlacierBlock": 0,
+        "berlinBlock": 0,
+        "londonBlock": 0,
+        "arrowGlacierBlock": 0,
+        "grayGlacierBlock": 0,
+        "mergeNetsplitBlock": 0,
+        "shanghaiTime": 0,
+        "cancunTime": 0,
+        "bedrockBlock": 0,
+        "regolithTime": 0,
+        "canyonTime": 0,
+        "ecotoneTime": 0,
+        "fjordTime": 0,
+        "graniteTime": 0,
+        "holoceneTime": 1732633200,
+        "terminalTotalDifficulty": 0,
+        "terminalTotalDifficultyPassed": true,
+        "optimism": {
+            "eip1559Elasticity": 6,
+            "eip1559Denominator": 50,
+            "eip1559DenominatorCanyon": 250
+        }
+    },
+    "nonce": "0x0",
+    "timestamp": "0x66edad4c",
+    "extraData": "0x424544524f434b",
+    "gasLimit": "0x1c9c380",
+    "difficulty": "0x0",
+    "mixHash": "0x0000000000000000000000000000000000000000000000000000000000000000",
+    "coinbase": "0x4200000000000000000000000000000000000011",
+    "alloc": {},
+    "number": "0x0",
+    "gasUsed": "0x0",
+    "parentHash": "0x0000000000000000000000000000000000000000000000000000000000000000",
+    "baseFeePerGas": "0x3b9aca00",
+    "excessBlobGas": "0x0",
+    "blobGasUsed": "0x0"
+}
+        "#;
+
+        let genesis: Genesis = serde_json::from_str(geth_genesis).unwrap();
+        let chainspec = OpChainSpec::from_genesis(genesis);
+        assert!(chainspec.is_holocene_active_at_timestamp(1732633200));
+    }
 }