diff --git a/lib/ain-ocean/src/api/address.rs b/lib/ain-ocean/src/api/address.rs
index 0e4dcd35fa..e41ff07373 100644
--- a/lib/ain-ocean/src/api/address.rs
+++ b/lib/ain-ocean/src/api/address.rs
@@ -458,14 +458,17 @@ async fn list_transaction_unspent(
                 msg: format!("Invalid height: {}", height),
             })?;
             let txid = Txid::from_str(txid)?;
-            let n = n.parse::<usize>()?;
-            Ok::<([u8; 4], Txid, usize), Error>((height, txid, n))
+            let decoded_n = hex::decode(n)?;
+            let n = decoded_n.try_into().map_err(|_| Error::Other {
+                msg: format!("Invalid txno: {}", n)
+            })?;
+            Ok::<([u8; 4], Txid, [u8; 8]), Error>((height, txid, n))
         })
         .transpose()?
         .unwrap_or((
-            [0u8, 0u8, 0u8, 0u8],
+            [0u8; 4],
             Txid::from_byte_array([0x00u8; 32]),
-            usize::default(),
+            [0u8; 8],
         ));
 
     let res = ctx
diff --git a/lib/ain-ocean/src/indexer/mod.rs b/lib/ain-ocean/src/indexer/mod.rs
index fbc140fc0f..1824e285f4 100644
--- a/lib/ain-ocean/src/indexer/mod.rs
+++ b/lib/ain-ocean/src/indexer/mod.rs
@@ -160,7 +160,7 @@ fn index_script_unspent_vin(
     vin: &VinStandard,
     ctx: &Context,
 ) -> Result<()> {
-    let key = (ctx.block.height.to_be_bytes(), vin.txid, vin.vout);
+    let key = (ctx.block.height.to_be_bytes(), vin.txid, vin.vout.to_be_bytes());
     let id = services.script_unspent.by_key.get(&key)?;
     if let Some(id) = id {
         services.script_unspent.by_id.delete(&id)?;
@@ -255,8 +255,8 @@ fn index_script_unspent_vout(services: &Arc<Services>, vout: &Vout, ctx: &Contex
         },
     };
 
-    let id = (hid, block.height.to_be_bytes(), tx.txid, vout.n);
-    let key = (block.height.to_be_bytes(), tx.txid, vout.n);
+    let id = (hid, block.height.to_be_bytes(), tx.txid, vout.n.to_be_bytes());
+    let key = (block.height.to_be_bytes(), tx.txid, vout.n.to_be_bytes());
     services.script_unspent.by_key.put(&key, &id)?;
     services.script_unspent.by_id.put(&id, &script_unspent)?;
     Ok(())
@@ -458,12 +458,12 @@ fn invalidate_script_unspent_vin(
         hid,
         transaction.block.height.to_be_bytes(),
         transaction.txid,
-        vout.n,
+        vout.n.to_be_bytes(),
     );
     let key = (
         transaction.block.height.to_be_bytes(),
         transaction.txid,
-        vout.n,
+        vout.n.to_be_bytes(),
     );
 
     services.script_unspent.by_key.put(&key, &id)?;
@@ -496,8 +496,8 @@ fn invalidate_script_unspent_vout(
     vout: &Vout,
 ) -> Result<()> {
     let hid = as_sha256(&vout.script_pub_key.hex);
-    let id = (hid, ctx.block.height.to_be_bytes(), ctx.tx.txid, vout.n);
-    let key = (ctx.block.height.to_be_bytes(), ctx.tx.txid, vout.n);
+    let id = (hid, ctx.block.height.to_be_bytes(), ctx.tx.txid, vout.n.to_be_bytes());
+    let key = (ctx.block.height.to_be_bytes(), ctx.tx.txid, vout.n.to_be_bytes());
     services.script_unspent.by_id.delete(&id)?;
     services.script_unspent.by_key.delete(&key)?;
 
diff --git a/lib/ain-ocean/src/model/script_unspent.rs b/lib/ain-ocean/src/model/script_unspent.rs
index c088751976..0bf270cd8b 100644
--- a/lib/ain-ocean/src/model/script_unspent.rs
+++ b/lib/ain-ocean/src/model/script_unspent.rs
@@ -3,8 +3,8 @@ use serde::{Deserialize, Serialize};
 
 use super::BlockContext;
 
-pub type ScriptUnspentId = ([u8; 32], [u8; 4], Txid, usize); // hid + block.height + txid + vout_index
-pub type ScriptUnspentKey = ([u8; 4], Txid, usize); // block.height + txid + vout_index, ps: key is required in index_script_unspent_vin
+pub type ScriptUnspentId = ([u8; 32], [u8; 4], Txid, [u8; 8]); // hid + block.height + txid + vout_index
+pub type ScriptUnspentKey = ([u8; 4], Txid, [u8; 8]); // block.height + txid + vout_index, ps: key is required in index_script_unspent_vin
 
 #[derive(Debug, Serialize, Deserialize)]
 pub struct ScriptUnspent {