diff --git a/src/api.rs b/src/api.rs
index 06713bc..56955af 100644
--- a/src/api.rs
+++ b/src/api.rs
@@ -1115,7 +1115,7 @@ pub fn create_transaction(addresses: Vec<String>, fee_rate: u32) -> ApiResult<Ap
     // We mark the utxos in the inputs as spent to prevent accidental double spends
     for input in &unsigned_tx.unsigned_tx.as_ref().unwrap().input {
         if let Some(output) = outputs.get_mut(&input.previous_output) {
-            output.spend_status = OutputSpendStatus::Spent(new_txid.to_string());
+            output.spend_status = OutputSpendStatus::Spent(new_txid.to_byte_array());
         }
     }