diff --git a/src/core/prefixer.rs b/src/core/prefixer.rs
index 0c6a95a..270b4d5 100644
--- a/src/core/prefixer.rs
+++ b/src/core/prefixer.rs
@@ -599,7 +599,7 @@ mod test {
         let prefixer = Prefixer::new(Some(&ked), None, Some(code), None, None, None, None).unwrap();
 
         let mut map = ked.to_map().unwrap();
-        map.remove("k");
+        map.swap_remove("k");
         ked = dat!(&map);
 
         assert!(!prefixer.verify(&ked, None).unwrap());
diff --git a/src/core/saider.rs b/src/core/saider.rs
index d9d61e8..abd3cf0 100644
--- a/src/core/saider.rs
+++ b/src/core/saider.rs
@@ -76,7 +76,7 @@ fn derive(
     let mut map = sad.to_map()?;
     for key in ignore.unwrap_or(&[]) {
         if map.contains_key(*key) {
-            map.remove(*key);
+            map.swap_remove(*key);
         }
     }
     let ser = dat!(&map);