diff --git a/mm2src/coins/eth.rs b/mm2src/coins/eth.rs
index ef1d57968c..deb2d27ab9 100644
--- a/mm2src/coins/eth.rs
+++ b/mm2src/coins/eth.rs
@@ -157,6 +157,8 @@ mod eip1559_gas_fee;
 pub(crate) use eip1559_gas_fee::FeePerGasEstimated;
 use eip1559_gas_fee::{BlocknativeGasApiCaller, FeePerGasSimpleEstimator, GasApiConfig, GasApiProvider,
                       InfuraGasApiCaller};
+use mm2_number::num_bigint::ToBigInt;
+
 pub(crate) mod eth_swap_v2;
 
 /// https://github.com/artemii235/etomic-swap/blob/master/contracts/EtomicSwap.sol
@@ -917,7 +919,11 @@ pub async fn withdraw_erc1155(ctx: MmArc, withdraw_type: WithdrawErc1155) -> Wit
     let amount_dec = if withdraw_type.max {
         wallet_amount.clone()
     } else {
-        withdraw_type.amount.unwrap_or_else(|| 1.into())
+        let amount = withdraw_type.amount.unwrap_or_else(|| BigUint::from(1u32));
+        let bigint = amount
+            .to_bigint()
+            .ok_or_else(|| WithdrawError::InternalError("Failed to convert BigUint to BigInt".to_string()))?;
+        BigDecimal::from(bigint)
     };
 
     if amount_dec > wallet_amount {
diff --git a/mm2src/coins/nft/nft_structs.rs b/mm2src/coins/nft/nft_structs.rs
index f772b92f56..52febc5270 100644
--- a/mm2src/coins/nft/nft_structs.rs
+++ b/mm2src/coins/nft/nft_structs.rs
@@ -438,7 +438,8 @@ pub struct WithdrawErc1155 {
     #[serde(deserialize_with = "deserialize_token_id")]
     pub(crate) token_id: BigUint,
     /// Optional amount of the token to withdraw. Defaults to 1 if not specified.
-    pub(crate) amount: Option<BigDecimal>,
+    #[serde(deserialize_with = "deserialize_opt_biguint")]
+    pub(crate) amount: Option<BigUint>,
     /// If set to `true`, withdraws the maximum amount available. Overrides the `amount` field.
     #[serde(default)]
     pub(crate) max: bool,
@@ -806,6 +807,19 @@ where
     BigUint::from_str(&s).map_err(serde::de::Error::custom)
 }
 
+/// Custom deserialization function for optional BigUint.
+fn deserialize_opt_biguint<'de, D>(deserializer: D) -> Result<Option<BigUint>, D::Error>
+where
+    D: Deserializer<'de>,
+{
+    let opt: Option<String> = Option::deserialize(deserializer)?;
+    if let Some(s) = opt {
+        BigUint::from_str(&s).map(Some).map_err(serde::de::Error::custom)
+    } else {
+        Ok(None)
+    }
+}
+
 /// Request parameters for clearing NFT data from the database.
 #[derive(Debug, Deserialize)]
 pub struct ClearNftDbReq {