diff --git a/Cargo.toml b/Cargo.toml
index 8e0cff6d..b42e09f0 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -8,6 +8,8 @@ members = ["integration_test"]
 
 
 [dependencies]
+bitcoin = { version = "0.30.0", features=["serde"] }
+lightning-invoice = { version = "0.22.0", features=["serde"] }
 minreq = { version = "2.7.0", features = ["json-using-serde", "https"] }
 serde = { version = "1.0.160", features = ["derive"]}
 thiserror = "1.0.40"
diff --git a/src/cashu_mint.rs b/src/cashu_mint.rs
index 1cbc1008..abb584f8 100644
--- a/src/cashu_mint.rs
+++ b/src/cashu_mint.rs
@@ -1,3 +1,4 @@
+use lightning_invoice::Invoice;
 use url::Url;
 
 use crate::{
@@ -60,12 +61,10 @@ impl CashuMint {
     }
 
     /// Check Max expected fee [NUT-05]
-    pub async fn check_fees(&self, invoice: &str) -> Result<CheckFeesResponse, Error> {
+    pub async fn check_fees(&self, invoice: Invoice) -> Result<CheckFeesResponse, Error> {
         let url = self.url.join("checkfees")?;
 
-        let request = CheckFeesRequest {
-            pr: invoice.to_string(),
-        };
+        let request = CheckFeesRequest { pr: invoice };
 
         Ok(minreq::post(url)
             .with_json(&request)?
@@ -78,14 +77,14 @@ impl CashuMint {
     pub async fn melt(
         &self,
         proofs: Vec<Proof>,
-        invoice: &str,
+        invoice: Invoice,
         outputs: Option<Vec<BlindedMessage>>,
     ) -> Result<MeltResposne, Error> {
         let url = self.url.join("melt")?;
 
         let request = MeltRequest {
             proofs,
-            pr: invoice.to_string(),
+            pr: invoice,
             outputs,
         };
 
diff --git a/src/types.rs b/src/types.rs
index bc5d37d0..346168fa 100644
--- a/src/types.rs
+++ b/src/types.rs
@@ -2,6 +2,8 @@
 
 use std::collections::HashMap;
 
+use bitcoin::Amount;
+use lightning_invoice::Invoice;
 use serde::{Deserialize, Deserializer, Serialize, Serializer};
 
 /// Blinded Message [NUT-00]
@@ -18,8 +20,8 @@ pub struct BlindedMessage {
 #[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
 pub struct Promise {
     pub id: String,
-    /// Amount in satoshi
-    pub amount: u64,
+    #[serde(with = "bitcoin::amount::serde::as_sat")]
+    pub amount: Amount,
     /// blinded signature (C_) on the secret message `B_` of [BlindedMessage]
     #[serde(rename = "C_")]
     pub c: String,
@@ -56,7 +58,7 @@ pub struct MintKeySets {
 #[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
 pub struct RequestMintResponse {
     /// Bolt11 payment request
-    pub pr: String,
+    pub pr: Invoice,
     /// Hash of Invoice
     pub hash: String,
 }
@@ -84,7 +86,7 @@ pub struct CheckFeesResponse {
 #[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
 pub struct CheckFeesRequest {
     /// Lighting Invoice
-    pub pr: String,
+    pub pr: Invoice,
 }
 
 /// Melt Request [NUT-05]
@@ -92,7 +94,7 @@ pub struct CheckFeesRequest {
 pub struct MeltRequest {
     pub proofs: Vec<Proof>,
     /// bollt11
-    pub pr: String,
+    pub pr: Invoice,
     /// Blinded Message that can be used to return change [NUT-08]
     /// Amount feild of blindedMessages `SHOULD` be set to zero
     pub outputs: Option<Vec<BlindedMessage>>,