diff --git a/Cargo.lock b/Cargo.lock
index f4acf157..f1218059 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1548,9 +1548,8 @@ checksum = "bceb57dc07c92cdae60f5b27b3fa92ecaaa42fe36c55e22dbfb0b44893e0b1f7"
 
 [[package]]
 name = "sourmash"
-version = "0.15.2"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9a73bae93170d8d0f816e18b6a630d76e134b90958850985ee2f0fb2f641d4de"
+version = "0.16.0"
+source = "git+https://github.com/sourmash-bio/sourmash.git?branch=refactor_rs_downsample#62f03eb3de8f4b05307efad74f321ced04de40f1"
 dependencies = [
  "az",
  "byteorder",
diff --git a/Cargo.toml b/Cargo.toml
index 5f8cc0b4..5e28367b 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -12,6 +12,8 @@ crate-type = ["cdylib"]
 pyo3 = { version = "0.22.3", features = ["extension-module", "anyhow"] }
 rayon = "1.10.0"
 serde = { version = "1.0.210", features = ["derive"] }
+#sourmash = { version = "0.15.2", features = ["branchwater"] }
+sourmash = { git = "https://github.com/sourmash-bio/sourmash.git", branch = "refactor_rs_downsample", features = ["branchwater"] }
 serde_json = "1.0.128"
 sourmash = { version = "0.15.2", features = ["branchwater"] }
 niffler = "2.4.0"
diff --git a/src/manysearch.rs b/src/manysearch.rs
index fcd691d3..a6c320a0 100644
--- a/src/manysearch.rs
+++ b/src/manysearch.rs
@@ -220,6 +220,7 @@ fn downsample_and_inflate_abundances(
     // avoid downsampling if we can
     if against_scaled != query_scaled {
         let against_ds = against
+            .clone()
             .downsample_scaled(query.scaled())
             .expect("cannot downsample sketch");
         (abunds, sum_weighted) = query.inflated_abundances(&against_ds)?;
diff --git a/src/python/tests/test_fastmultigather.py b/src/python/tests/test_fastmultigather.py
index 7bc54b3c..643799b9 100644
--- a/src/python/tests/test_fastmultigather.py
+++ b/src/python/tests/test_fastmultigather.py
@@ -992,7 +992,7 @@ def test_indexed_full_output(runtmp):
     # check a few columns
     average_ani = set(df['average_containment_ani'])
     avg_ani = set([round(x, 4) for x in average_ani])
-    assert avg_ani == {0.8502, 0.8584, 0.8602}
+    assert avg_ani == {0.9221, 0.9306, 0.9316} # @CTB check against py gather
 
     f_unique_weighted = set(df['f_unique_weighted'])
     f_unique_weighted = set([round(x, 4) for x in f_unique_weighted])
@@ -1000,7 +1000,7 @@ def test_indexed_full_output(runtmp):
 
     unique_intersect_bp = set(df['unique_intersect_bp'])
     unique_intersect_bp = set([round(x,4) for x in unique_intersect_bp])
-    assert unique_intersect_bp == {44000, 18000, 22000}
+    assert unique_intersect_bp == {4400000, 1800000, 2200000}
 
 
 def test_nonindexed_full_vs_sourmash_gather(runtmp):
diff --git a/src/utils/mod.rs b/src/utils/mod.rs
index 093344e9..48157179 100644
--- a/src/utils/mod.rs
+++ b/src/utils/mod.rs
@@ -452,7 +452,10 @@ pub fn load_sketches_above_threshold(
             if let Ok(against_sig) = coll.sig_from_record(against_record) {
                 if let Some(against_mh) = against_sig.minhash() {
                     // downsample against_mh, but keep original md5sum
-                    let against_mh_ds = against_mh.downsample_scaled(query.scaled()).unwrap();
+                    let against_mh_ds = against_mh
+                        .clone()
+                        .downsample_scaled(query.scaled())
+                        .unwrap();
                     if let Ok(overlap) = against_mh_ds.count_common(query, false) {
                         if overlap >= threshold_hashes {
                             let result = PrefetchResult {