diff --git a/src/bdk.udl b/src/bdk.udl
index 27c554d..e3ab62e 100644
--- a/src/bdk.udl
+++ b/src/bdk.udl
@@ -120,6 +120,10 @@ interface BlockchainConfig {
   Esplora(EsploraConfig config);
 };
 
+callback interface BdkProgress {
+  void update(f32 progress, string? message);
+};
+
 interface OnlineWallet {
   [Throws=BdkError]
   constructor(string descriptor, string? change_descriptor, Network network, DatabaseConfig database_config, BlockchainConfig blockchain_config);
@@ -136,7 +140,7 @@ interface OnlineWallet {
   // OnlineWalletInterface
   Network get_network();
   [Throws=BdkError]
-  void sync(u32? max_address_param);
+  void sync(BdkProgress progress_update, u32? max_address_param);
   [Throws=BdkError]
   string broadcast([ByRef] PartiallySignedBitcoinTransaction psbt);
 };
diff --git a/src/lib.rs b/src/lib.rs
index 9faf5f7..e19ab21 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -154,10 +154,13 @@ pub trait BdkProgress: Send + Sync {
     fn update(&self, progress: f32, message: Option<String>);
 }
 
-struct BdkProgressHolder {}
+struct BdkProgressHolder {
+    progress_update: Box<dyn BdkProgress>,
+}
 
 impl Progress for BdkProgressHolder {
-    fn update(&self, _progress: f32, _message: Option<String>) -> Result<(), Error> {
+    fn update(&self, progress: f32, message: Option<String>) -> Result<(), Error> {
+        self.progress_update.update(progress, message);
         Ok(())
     }
 }
@@ -235,11 +238,16 @@ impl OnlineWallet {
         self.wallet.lock().unwrap().network()
     }
 
-    fn sync(&self, max_address_param: Option<u32>) -> Result<(), BdkError> {
+    fn sync(
+        &self,
+        progress_update: Box<dyn BdkProgress>,
+        max_address_param: Option<u32>,
+    ) -> Result<(), BdkError> {
+        progress_update.update(21.0, Some("message".to_string()));
         self.wallet
             .lock()
             .unwrap()
-            .sync(BdkProgressHolder {}, max_address_param)
+            .sync(BdkProgressHolder { progress_update }, max_address_param)
     }
 
     fn broadcast<'a>(&self, psbt: &'a PartiallySignedBitcoinTransaction) -> Result<String, Error> {