diff --git a/proto/service.proto b/proto/service.proto
index 49f97ea..d0548df 100644
--- a/proto/service.proto
+++ b/proto/service.proto
@@ -20,6 +20,7 @@ message BlockID {
 message BlockRange {
     BlockID start = 1;
     BlockID end = 2;
+    uint64 spamFilterThreshold = 3;
 }
 
 // A TxFilter contains the information needed to identify a particular
diff --git a/src/chain.rs b/src/chain.rs
index 076c692..3faf043 100644
--- a/src/chain.rs
+++ b/src/chain.rs
@@ -152,6 +152,7 @@ pub async fn download_chain(
     start_height: u32,
     end_height: u32,
     mut prev_hash: Option<[u8; 32]>,
+    max_cost: u32,
     blocks_tx: Sender<Blocks>,
     cancel: &'static Mutex<bool>,
 ) -> anyhow::Result<()> {
@@ -170,6 +171,7 @@ pub async fn download_chain(
             height: end_height as u64,
             hash: vec![],
         }),
+        spam_filter_threshold: max_cost as u64,
     };
     *DOWNLOADED_BYTES.lock().unwrap() = 0;
     *TRIAL_DECRYPTIONS.lock().unwrap() = 0;
@@ -201,14 +203,19 @@ pub async fn download_chain(
         prev_hash = Some(ph);
         for b in block.vtx.iter_mut() {
             b.actions.clear(); // don't need Orchard actions
+            let mut skipped = false;
             for co in b.outputs.iter_mut() {
                 if co.epk.is_empty() {
+                    skipped = true;
                     co.epk = vec![0; 32];
                 }
                 if co.ciphertext.is_empty() {
                     co.ciphertext = vec![0; 52];
                 }
             }
+            if skipped {
+                log::info!("Output skipped {}", b.outputs.len());
+            }
         }
 
         let block_output_count: usize = block.vtx.iter().map(|tx| tx.outputs.len()).sum();
diff --git a/src/generated/cash.z.wallet.sdk.rpc.rs b/src/generated/cash.z.wallet.sdk.rpc.rs
index 10f5eb7..d200197 100644
--- a/src/generated/cash.z.wallet.sdk.rpc.rs
+++ b/src/generated/cash.z.wallet.sdk.rpc.rs
@@ -109,6 +109,8 @@ pub struct BlockRange {
     pub start: ::core::option::Option<BlockId>,
     #[prost(message, optional, tag="2")]
     pub end: ::core::option::Option<BlockId>,
+    #[prost(uint64, tag="3")]
+    pub spam_filter_threshold: u64,
 }
 /// A TxFilter contains the information needed to identify a particular
 /// transaction: either a block and an index, or a direct transaction hash.
diff --git a/src/main/rpc.rs b/src/main/rpc.rs
index 23c364a..0f2447f 100644
--- a/src/main/rpc.rs
+++ b/src/main/rpc.rs
@@ -11,7 +11,7 @@ use rocket::{response, Request, Response, State};
 use std::collections::HashMap;
 use std::fs::File;
 use std::io::{BufReader, Read};
-use std::sync::atomic::AtomicBool;
+use std::sync::Mutex;
 use thiserror::Error;
 use warp_api_ffi::api::payment::{Recipient, RecipientMemo};
 use warp_api_ffi::api::payment_uri::PaymentURI;
@@ -21,7 +21,7 @@ use warp_api_ffi::{
 };
 
 lazy_static! {
-    static ref SYNC_CANCELED: AtomicBool = AtomicBool::new(false);
+    static ref SYNC_CANCELED: Mutex<bool> = Mutex::new(false);
 }
 
 #[derive(Error, Debug)]
diff --git a/src/scan.rs b/src/scan.rs
index a34bc79..1f49e4d 100644
--- a/src/scan.rs
+++ b/src/scan.rs
@@ -94,6 +94,7 @@ pub async fn sync_async(
             start_height,
             end_height,
             prev_hash,
+            max_cost,
             decryptor_tx,
             cancel,
         )