diff --git a/Cargo.toml b/Cargo.toml
index 095bf55..d6b89c2 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -84,3 +84,7 @@ required-features = ["client", "server"]
 [[test]]
 name = "lud16"
 required-features = ["client", "server"]
+
+[[test]]
+name = "lud21"
+required-features = ["client", "server"]
diff --git a/README.md b/README.md
index 51052d5..c9862ac 100644
--- a/README.md
+++ b/README.md
@@ -29,7 +29,7 @@ This library works as a toolkit so you can serve and make your LNURL requests wi
 - [LUD-18](https://github.com/lnurl/luds/blob/luds/18.md): 🆘 core 🆘 client 🆘 server 🆘 tests
 - [LUD-19](https://github.com/lnurl/luds/blob/luds/19.md): 🆘 core 🆘 client 🆘 server 🆘 tests
 - [LUD-20](https://github.com/lnurl/luds/blob/luds/20.md): ✅ core ✅ client ✅ server ⚠️ tests
-- [LUD-21 *proposal*](https://github.com/lnurl/luds/blob/8580e3c8cbfd8fc95a6c0e5f7fcb5b048a0d5b61/21.md): ⚠️ core ⚠️ client ⚠️ server 🆘 tests
+- [LUD-21 *proposal*](https://github.com/lnurl/luds/blob/8580e3c8cbfd8fc95a6c0e5f7fcb5b048a0d5b61/21.md): ✅ core ✅ client ✅ server ✅ tests
 
 ###### Soon. ™
 
diff --git a/tests/lud21.rs b/tests/lud21.rs
new file mode 100644
index 0000000..681d1a9
--- /dev/null
+++ b/tests/lud21.rs
@@ -0,0 +1,106 @@
+#[tokio::test]
+async fn test() {
+    let listener = tokio::net::TcpListener::bind("0.0.0.0:0")
+        .await
+        .expect("net");
+
+    let addr = listener.local_addr().expect("addr");
+
+    let query_url = format!("http://{addr}/lnurlp");
+    let callback_url = url::Url::parse(&format!("http://{addr}/lnurlp/callback")).expect("url");
+
+    let router = lnurlkit::Server::default()
+        .pay_request(
+            move |_| {
+                let callback = callback_url.clone();
+                async {
+                    Ok(lnurlkit::pay::server::Entrypoint {
+                        callback,
+                        short_description: String::from("today i become death"),
+                        long_description: Some(String::from("the destroyer of worlds")),
+                        jpeg: None,
+                        png: None,
+                        comment_size: None,
+                        min: 314,
+                        max: 315,
+                        identifier: None,
+                        email: None,
+                        currencies: Some(vec![
+                            lnurlkit::pay::Currency {
+                                code: String::from("BRL"),
+                                name: String::from("Reais"),
+                                symbol: String::from("R$"),
+                                decimals: 2,
+                                multiplier: 314.15,
+                                convertible: true,
+                            },
+                            lnurlkit::pay::Currency {
+                                code: String::from("USD"),
+                                name: String::from("Dólar"),
+                                symbol: String::from("$"),
+                                decimals: 3,
+                                multiplier: 123.321,
+                                convertible: false,
+                            },
+                        ]),
+                    })
+                }
+            },
+            |req: lnurlkit::pay::server::Callback| async move {
+                Ok(lnurlkit::pay::server::CallbackResponse {
+                    pr: format!("pierre:{:?}:{:?}", req.amount, req.convert),
+                    disposable: false,
+                    success_action: None,
+                })
+            },
+        )
+        .build();
+
+    tokio::spawn(async move {
+        axum::serve(listener, router).await.expect("serve");
+    });
+
+    let client = lnurlkit::Client::default();
+
+    let lnurl = bech32::encode(
+        "lnurl",
+        bech32::ToBase32::to_base32(&query_url),
+        bech32::Variant::Bech32,
+    )
+    .expect("lnurl");
+
+    let queried = client.entrypoint(&lnurl).await.expect("query");
+    let lnurlkit::client::Entrypoint::Pay(pr) = queried else {
+        panic!("not pay request");
+    };
+
+    let currencies = pr.core.currencies.as_ref().unwrap();
+
+    assert_eq!(currencies[0].code, "BRL");
+    assert_eq!(currencies[0].name, "Reais");
+    assert_eq!(currencies[0].symbol, "R$");
+    assert_eq!(currencies[0].decimals, 2);
+    assert!((currencies[0].multiplier - 314.15).abs() < f64::EPSILON);
+    assert!(currencies[0].convertible);
+
+    assert_eq!(currencies[1].code, "USD");
+    assert_eq!(currencies[1].name, "Dólar");
+    assert_eq!(currencies[1].symbol, "$");
+    assert_eq!(currencies[1].decimals, 3);
+    assert!((currencies[1].multiplier - 123.321).abs() < f64::EPSILON);
+    assert!(!currencies[1].convertible);
+
+    let invoice = pr
+        .invoice(
+            &lnurlkit::pay::Amount::Currency(String::from("USD"), 314),
+            None,
+            Some("BRL"),
+        )
+        .await
+        .expect("callback");
+
+    assert_eq!(
+        &invoice.pr as &str,
+        "pierre:Currency(\"USD\", 314):Some(\"BRL\")"
+    );
+}