diff --git a/bdk-ffi/src/bdk.udl b/bdk-ffi/src/bdk.udl
index 6e44a74..3dbaa55 100644
--- a/bdk-ffi/src/bdk.udl
+++ b/bdk-ffi/src/bdk.udl
@@ -333,11 +333,13 @@ interface SyncRequest {
   SyncRequest inspect_spks(SyncScriptInspector inspector);
 };
 
-callback interface SyncScriptInspector {
+[Trait, WithForeign]
+interface SyncScriptInspector {
   void inspect(Script script, u64 total);
 };
 
-callback interface FullScanScriptInspector {
+[Trait, WithForeign]
+interface FullScanScriptInspector {
   void inspect(KeychainKind keychain, u32 index, Script script);
 };
 
diff --git a/bdk-ffi/src/types.rs b/bdk-ffi/src/types.rs
index 8960824..4e0b03b 100644
--- a/bdk-ffi/src/types.rs
+++ b/bdk-ffi/src/types.rs
@@ -127,7 +127,7 @@ pub struct SyncRequest(pub(crate) Mutex<Option<BdkSyncRequest>>);
 impl SyncRequest {
     pub fn inspect_spks(
         &self,
-        inspector: Box<dyn SyncScriptInspector>,
+        inspector: Arc<dyn SyncScriptInspector>,
     ) -> Result<Arc<Self>, InspectError> {
         let mut guard = self.0.lock().unwrap();
         if let Some(sync_request) = guard.take() {
@@ -145,7 +145,7 @@ impl SyncRequest {
 impl FullScanRequest {
     pub fn inspect_spks_for_all_keychains(
         &self,
-        inspector: Box<dyn FullScanScriptInspector>,
+        inspector: Arc<dyn FullScanScriptInspector>,
     ) -> Result<Arc<Self>, InspectError> {
         let mut guard = self.0.lock().unwrap();
         if let Some(full_scan_request) = guard.take() {