diff --git a/chain/rust/src/genesis/shelley/config.rs b/chain/rust/src/genesis/shelley/config.rs
index 45eade5a..94aab8c1 100644
--- a/chain/rust/src/genesis/shelley/config.rs
+++ b/chain/rust/src/genesis/shelley/config.rs
@@ -18,7 +18,7 @@ pub struct ShelleyGenesisData {
     pub network_magic: u64,
     pub protocol_params: ShelleyGenesisProtocolParameters,
     pub security_param: u64,
-    pub slot_length: u64,
+    pub slot_length: Fraction,
     pub slots_per_kes_period: u64,
     pub staking: Option<ShelleyGenesisStaking>,
     pub system_start: chrono::DateTime<chrono::Utc>,
diff --git a/chain/rust/src/genesis/shelley/parse.rs b/chain/rust/src/genesis/shelley/parse.rs
index 0dfa4415..1ec4077e 100644
--- a/chain/rust/src/genesis/shelley/parse.rs
+++ b/chain/rust/src/genesis/shelley/parse.rs
@@ -172,7 +172,7 @@ pub fn parse_genesis_data<R: Read>(
             tau: fraction::Fraction::from_str(&data.protocolParams.tau).unwrap(),
         },
         security_param: data.securityParam,
-        slot_length: data.slotLength,
+        slot_length: fraction::Fraction::from_str(&data.slotLength).unwrap(),
         slots_per_kes_period: data.slotsPerKESPeriod,
         staking,
         system_start: data.systemStart.parse().expect("Failed to parse date"),
@@ -193,6 +193,10 @@ mod test {
         include_str!("./test_data/test.json")
     }
 
+    fn get_test_genesis_data_yaci() -> &'static str {
+        include_str!("./test_data/test-yaci.json")
+    }
+
     #[test]
     fn calc_address_txid() {
         let hash = redeem_address_to_txid(
@@ -223,4 +227,9 @@ mod test {
             3000000000000000u64
         );
     }
+
+    #[test]
+    fn parse_test_genesis_yaci_files() {
+        super::parse_genesis_data(get_test_genesis_data_yaci().as_bytes()).unwrap();
+    }
 }
diff --git a/chain/rust/src/genesis/shelley/raw.rs b/chain/rust/src/genesis/shelley/raw.rs
index c89fd6d4..58a0db72 100644
--- a/chain/rust/src/genesis/shelley/raw.rs
+++ b/chain/rust/src/genesis/shelley/raw.rs
@@ -22,7 +22,8 @@ pub struct ShelleyGenesisData {
     pub networkMagic: u64,
     pub protocolParams: ShelleyGenesisProtocolParameters,
     pub securityParam: u64,
-    pub slotLength: u64,
+    #[serde(deserialize_with = "deserialize_string_from_number")]
+    pub slotLength: String,
     pub slotsPerKESPeriod: u64,
     pub staking: Option<ShelleyGenesisStaking>,
     pub systemStart: String,
diff --git a/chain/rust/src/genesis/shelley/test_data/test-yaci.json b/chain/rust/src/genesis/shelley/test_data/test-yaci.json
new file mode 100644
index 00000000..6c2585e1
--- /dev/null
+++ b/chain/rust/src/genesis/shelley/test_data/test-yaci.json
@@ -0,0 +1,92 @@
+{
+  "activeSlotsCoeff" : 1.0,
+  "epochLength" : 600,
+  "genDelegs" : {
+    "337bc5ef0f1abf205624555c13a37258c42b46b1259a6b1a6d82574e" : {
+      "delegate" : "41fd6bb31f34469320aa47cf6ccc3918e58a06d60ea1f2361efe2458",
+      "vrf" : "7053e3ecd2b19db13e5338aa75fb518fc08b6c218f56ad65760d3eb074be95d4"
+    }
+  },
+  "initialFunds" : {
+    "00c8c47610a36034aac6fc58848bdae5c278d994ff502c05455e3b3ee8f8ed3a0eea0ef835ffa7bbfcde55f7fe9d2cc5d55ea62cecb42bab3c" : 10000000000,
+    "004048ff89ca4f88e66598e620aa0c7128c2145d9a181ae9a4a81ca8e3e849af38840c5562dd382be37c9e76545c8191f9d8f6df1d20cfcee0" : 10000000000,
+    "00ca6e1b1f320d543a24adeabc0aa4627635c7349b639f86f74bdfdd78d31b28c9619a58b3792a7394ab85deb36889c4d7b0632c8167b855d2" : 10000000000,
+    "0007d781fe8e33883e371f9550c2f1087321fc32e06e80b65e349ccb027702d6880e86e77a0520efa37ede45002a1de43b68692e175b742e67" : 10000000000,
+    "00627b2598dd71129167825160c564067d1d245e79cc237094815c5cb2b125e30ec2f4ce4059a069e08c3cd82cdfc9451bfb22487f8a25ceef" : 10000000000,
+    "00c6cf7bd50f37f7e4cc161fc00f07e9b2226ba5552ccaf30d315fa0135bbc8cbd9ab5379f368fc8d3500c37a9d14074cc6ddad89e3686f0e0" : 10000000000,
+    "005164ab186715c86378020956d892cf72f67636b78967d67cfe7360479130dc89cf7a9bc89109f939956b66f93293ade4c3920b72fd40beea" : 10000000000,
+    "003dd38742e9848c6f12c13ddb1f9464fc0ce0bb92102768087975317e5a9f869fcd913562c9b0e0f01f77e5359ea780d37f9355f9702eff8b" : 10000000000,
+    "0088e7e670b45cab2322b518ef7b6f66d30aec0d923dc463e467091a790f67796b9fa71224f2846cebbcf4950c11e040ee124d30f6e164bcd5" : 10000000000,
+    "00c70b8421617802d3f23956cab1957e1d306cd4808589b41760e97927ebfd6053ba12b38288b2b6d5d4c4618d6a8ce59d50580e9c6f704af5" : 10000000000,
+    "00c0933b8238f6f3332e48c34cf1a8e0555943b33cd4abc53aefb7d6124b7ce40dd496bdc02b34602f3a773ff7cccee873991e4c8866f3a70b" : 10000000000,
+    "0069f7d7289de2f01cd1e0265ac5be943b41775abae0ce6b3eac0edee0ce9cadb7cdec2bded3ef8a7bbe3352869bfc1387754c9ee6b1782d9c" : 10000000000,
+    "00709a7070005c652c27df73dbbde3319a90b127bea96aded1c5fb87a59c51dbcf90fa890174497f3f66a0dad06eb7f131e06567995e9c50a5" : 10000000000,
+    "00fc576df3a279885a7a4d0fc500372daa1d96f26c6763542ecd2ad8551753024adea37c134edebb68dc0cfaed5a7009e8305fe1fed8d0ccd1" : 10000000000,
+    "003346a630e6972bf38cce87219db1d63061e7cd324cad88c18e504f2990cac68e973f51256ca938683fa4ea12173d7d047d940fbb883bd0e8" : 10000000000,
+    "0028b862d001e6a64a02b3560cbc532eab4557593477c39cc523e0b9fc527100898c11e731194171b908aad463770d6cbf7ec8871c4cb1e518" : 10000000000,
+    "005e0e57040b06e9d71e0f28f126262838a68db0b52b4fd1b3877dda2203d5d7d4f19c5ee3a1ed51bb670779de19d40aaff2e5e9468cc05c5e" : 10000000000,
+    "00367f65ab69b1e6715c8d5a14964214c9505ed17032266b3209a2c40dcbae9a2a881e603ff39d36e987bacfb87ee98051f222c5fe3efd350c" : 10000000000,
+    "00c5c4ca287f3b53948b5468e5e23b1c87fe61ce52c0d9afd65d070795038751a619d463e91eaed0a774ebdb2f8e12a01a378a153bc3627323" : 10000000000,
+    "00ef198fb7c35e1968308a0b75cfee54a46e13e86dd3354283300831d624165c357b5a0413906a0bfea8ba57587331f0836a186d632ed041b8" : 10000000000,
+    "60a0f1aa7dca95017c11e7e373aebcf0c4568cf47ec12b94f8eb5bba8b" : 3000000000000000,
+    "60ba957a0fff6816021b2afa7900beea68fd10f2d78fb5b64de0d2379c" : 3000000000000000,
+    "007290ea8fa9433c1045a4c8473959ad608e6c03a58c7de33bdbd3ce6f295b987135610616f3c74e11c94d77b6ced5ccc93a7d719cfb135062" : 300000000000,
+    "605276322ac7882434173dcc6441905f6737689bd309b68ad8b3614fd8" : 3000000000000000
+  },
+  "maxKESEvolutions" : 60,
+  "maxLovelaceSupply" : 45000000000000000,
+  "networkId" : "Testnet",
+  "networkMagic" : 42,
+  "protocolParams" : {
+    "a0" : 0.0,
+    "decentralisationParam" : 0,
+    "eMax" : 18,
+    "extraEntropy" : {
+      "tag" : "NeutralNonce"
+    },
+    "keyDeposit" : 2000000,
+    "maxBlockBodySize" : 90112,
+    "maxBlockHeaderSize" : 1100,
+    "maxTxSize" : 16384,
+    "minFeeA" : 44,
+    "minFeeB" : 155381,
+    "minPoolCost" : 170000000,
+    "minUTxOValue" : 1000000,
+    "nOpt" : 100,
+    "poolDeposit" : 500000000,
+    "protocolVersion" : {
+      "major" : 9,
+      "minor" : 0
+    },
+    "rho" : 0.003,
+    "tau" : 0.2
+  },
+  "securityParam" : 300,
+  "slotLength" : 1.0,
+  "slotsPerKESPeriod" : 129600,
+  "staking" : {
+    "pools" : {
+      "7301761068762f5900bde9eb7c1c15b09840285130f5b0f53606cc57" : {
+        "cost" : 340000000,
+        "margin" : 0,
+        "metadata" : null,
+        "owners" : [ ],
+        "pledge" : 0,
+        "publicKey" : "7301761068762f5900bde9eb7c1c15b09840285130f5b0f53606cc57",
+        "relays" : [ ],
+        "rewardAccount" : {
+          "credential" : {
+            "keyHash" : "11a14edf73b08a0a27cb98b2c57eb37c780df18fcfcf6785ed5df84a"
+          },
+          "network" : "Testnet"
+        },
+        "vrf" : "c2b62ffa92ad18ffc117ea3abeb161a68885000a466f9c71db5e4731d6630061"
+      }
+    },
+    "stake" : {
+      "295b987135610616f3c74e11c94d77b6ced5ccc93a7d719cfb135062" : "7301761068762f5900bde9eb7c1c15b09840285130f5b0f53606cc57"
+    }
+  },
+  "systemStart" : "2024-09-18T18:44:16.450192Z",
+  "updateQuorum" : 1
+}