diff --git a/src/lib.rs b/src/lib.rs
index 25bb348b..92b16718 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1818,7 +1818,7 @@ fn manysketch<P: AsRef<Path> + Sync>(
                         while let Some(record_result) = parser.next() {
                             match record_result {
                                 Ok(record) => {
-                                    for mut sig in &mut sigs {
+                                    for sig in &mut sigs {
                                         if moltype == "protein" {
                                             sig.add_protein(&record.seq()).unwrap();
                                         } else {