diff --git a/src/engine/db/mod.rs b/src/engine/db/mod.rs
index fd428a3..0b79c24 100644
--- a/src/engine/db/mod.rs
+++ b/src/engine/db/mod.rs
@@ -707,7 +707,11 @@ impl ChannelInfo {
                 '+' => adding = true,
                 '-' => adding = false,
                 m if m.is_ascii_alphabetic() => {
-                    if (m == 'r' || self.lock_on.contains(m)) && !adding && !readd.contains(m) {
+                    // A param mode (e.g. +f) is re-asserted whenever it's touched — set
+                    // as well as unset — so changing its param is reverted to the locked
+                    // one, not just re-added after a plain `-f`.
+                    let param_locked = self.lock_params.iter().any(|(c, _)| *c == m);
+                    if (m == 'r' || self.lock_on.contains(m)) && (!adding || param_locked) && !readd.contains(m) {
                         readd.push(m);
                     } else if self.lock_off.contains(m) && adding && !reremove.contains(m) {
                         reremove.push(m);
diff --git a/src/engine/db/tests.rs b/src/engine/db/tests.rs
index cf66719..487533b 100644
--- a/src/engine/db/tests.rs
+++ b/src/engine/db/tests.rs
@@ -764,6 +764,14 @@
         assert_eq!(info.enforce("-r"), Some("+r".to_string()));   // +r always locked
         assert_eq!(info.enforce("+m"), None);                     // unrelated mode ignored
 
+        // A param mode (+f): both a plain unset AND a changed param revert to the
+        // locked param — not just the unset case.
+        db.set_mlock_params("#chan", "ntf", "s", vec![('f', "kick:4:5s".to_string())]).unwrap();
+        let info = db.channel("#chan").unwrap();
+        assert_eq!(info.enforce("-f"), Some("+f kick:4:5s".to_string())); // unset re-added with param
+        assert_eq!(info.enforce("+f"), Some("+f kick:4:5s".to_string())); // changed param reverted
+        db.set_mlock("#chan", "nt", "s").unwrap(); // restore for the reopen check
+
         drop(db);
         let db = Db::open(&p, "local");
         assert_eq!(db.channel("#chan").unwrap().lock_modes(), "+rnt-s", "survives reopen");