diff --git a/bin/reth/src/args/utils.rs b/bin/reth/src/args/utils.rs
index 0f9ef5c6bb8e..ab195311088b 100644
--- a/bin/reth/src/args/utils.rs
+++ b/bin/reth/src/args/utils.rs
@@ -47,21 +47,47 @@ pub fn genesis_value_parser(s: &str) -> eyre::Result<Arc<ChainSpec>, eyre::Error
         "holesky" => HOLESKY.clone(),
         "dev" => DEV.clone(),
         _ => {
-            // both serialized Genesis and ChainSpec structs supported
-            let genesis: AllGenesisFormats =
-                // try to read json from path first
+            // try to read json from path first
+            let mut raw =
                 match fs::read_to_string(PathBuf::from(shellexpand::full(s)?.into_owned())) {
-                    Ok(raw) => serde_json::from_str(&raw)?,
+                    Ok(raw) => raw,
                     Err(io_err) => {
                         // valid json may start with "\n", but must contain "{"
                         if s.contains('{') {
-                            serde_json::from_str(s)?
+                            s.to_string()
                         } else {
                             return Err(io_err.into()) // assume invalid path
                         }
                     }
                 };
 
+            // The ethereum mainnet TTD is 58750000000000000000000, and geth serializes this
+            // without quotes, because that is how golang `big.Int`s marshal in JSON. Numbers
+            // are arbitrary precision in JSON, so this is valid JSON. This number is also
+            // greater than a `u64`.
+            //
+            // Unfortunately, serde_json only supports parsing up to `u64`, resorting to `f64`
+            // once `u64` overflows:
+            // <https://github.com/serde-rs/json/blob/4bc1eaa03a6160593575bc9bc60c94dba4cab1e3/src/de.rs#L1411-L1415>
+            // <https://github.com/serde-rs/json/blob/4bc1eaa03a6160593575bc9bc60c94dba4cab1e3/src/de.rs#L479-L484>
+            // <https://github.com/serde-rs/json/blob/4bc1eaa03a6160593575bc9bc60c94dba4cab1e3/src/de.rs#L102-L108>
+            //
+            // serde_json does have an arbitrary precision feature, but this breaks untagged
+            // enums in serde:
+            // <https://github.com/serde-rs/serde/issues/2230>
+            // <https://github.com/serde-rs/serde/issues/1183>
+            //
+            // To solve this, we surround the mainnet TTD with quotes, which our custom Visitor
+            // accepts.
+            if raw.contains("58750000000000000000000") &&
+                !raw.contains("\"58750000000000000000000\"")
+            {
+                raw = raw.replacen("58750000000000000000000", "\"58750000000000000000000\"", 1);
+            }
+
+            // both serialized Genesis and ChainSpec structs supported
+            let genesis: AllGenesisFormats = serde_json::from_str(&raw)?;
+
             Arc::new(genesis.into())
         }
     })
diff --git a/crates/primitives/src/chain/spec.rs b/crates/primitives/src/chain/spec.rs
index 81cce105c40c..9cebf52a8367 100644
--- a/crates/primitives/src/chain/spec.rs
+++ b/crates/primitives/src/chain/spec.rs
@@ -2253,6 +2253,27 @@ Post-merge hard forks (timestamp based):
         assert_eq!(genesis.config.cancun_time, Some(4661));
     }
 
+    #[test]
+    fn test_parse_cancun_genesis_all_formats() {
+        let s = r#"{"config":{"ethash":{},"chainId":1337,"homesteadBlock":0,"eip150Block":0,"eip155Block":0,"eip158Block":0,"byzantiumBlock":0,"constantinopleBlock":0,"petersburgBlock":0,"istanbulBlock":0,"berlinBlock":0,"londonBlock":0,"terminalTotalDifficulty":0,"terminalTotalDifficultyPassed":true,"shanghaiTime":0,"cancunTime":4661},"nonce":"0x0","timestamp":"0x0","extraData":"0x","gasLimit":"0x4c4b40","difficulty":"0x1","mixHash":"0x0000000000000000000000000000000000000000000000000000000000000000","coinbase":"0x0000000000000000000000000000000000000000","alloc":{"658bdf435d810c91414ec09147daa6db62406379":{"balance":"0x487a9a304539440000"},"aa00000000000000000000000000000000000000":{"code":"0x6042","storage":{"0x0000000000000000000000000000000000000000000000000000000000000000":"0x0000000000000000000000000000000000000000000000000000000000000000","0x0100000000000000000000000000000000000000000000000000000000000000":"0x0100000000000000000000000000000000000000000000000000000000000000","0x0200000000000000000000000000000000000000000000000000000000000000":"0x0200000000000000000000000000000000000000000000000000000000000000","0x0300000000000000000000000000000000000000000000000000000000000000":"0x0000000000000000000000000000000000000000000000000000000000000303"},"balance":"0x1","nonce":"0x1"},"bb00000000000000000000000000000000000000":{"code":"0x600154600354","storage":{"0x0000000000000000000000000000000000000000000000000000000000000000":"0x0000000000000000000000000000000000000000000000000000000000000000","0x0100000000000000000000000000000000000000000000000000000000000000":"0x0100000000000000000000000000000000000000000000000000000000000000","0x0200000000000000000000000000000000000000000000000000000000000000":"0x0200000000000000000000000000000000000000000000000000000000000000","0x0300000000000000000000000000000000000000000000000000000000000000":"0x0000000000000000000000000000000000000000000000000000000000000303"},"balance":"0x2","nonce":"0x1"}},"number":"0x0","gasUsed":"0x0","parentHash":"0x0000000000000000000000000000000000000000000000000000000000000000","baseFeePerGas":"0x3b9aca00"}"#;
+        let genesis: AllGenesisFormats = serde_json::from_str(s).unwrap();
+
+        // this should be the genesis format
+        let genesis = match genesis {
+            AllGenesisFormats::Geth(genesis) => genesis,
+            _ => panic!("expected geth genesis format"),
+        };
+
+        // assert that the alloc was picked up
+        let acc = genesis
+            .alloc
+            .get(&"0xaa00000000000000000000000000000000000000".parse::<Address>().unwrap())
+            .unwrap();
+        assert_eq!(acc.balance, U256::from(1));
+        // assert that the cancun time was picked up
+        assert_eq!(genesis.config.cancun_time, Some(4661));
+    }
+
     #[test]
     fn test_default_cancun_header_forkhash() {
         // set the gas limit from the hive test genesis according to the hash