diff --git a/rslib/src/deckconfig/update.rs b/rslib/src/deckconfig/update.rs
index 4647e05e3..ed2be846f 100644
--- a/rslib/src/deckconfig/update.rs
+++ b/rslib/src/deckconfig/update.rs
@@ -204,7 +204,7 @@ impl Collection {
                     .map(|c| c.inner.fsrs_enabled)
                     .unwrap_or_default();
                 let current_weights = current_config.map(|c| &c.inner.fsrs_weights);
-                if current_fsrs_on && (!previous_fsrs_on || previous_weights != current_weights) {
+                if current_fsrs_on != previous_fsrs_on || previous_weights != current_weights {
                     decks_needing_memory_recompute
                         .entry(current_config_id)
                         .or_default()
@@ -216,15 +216,16 @@ impl Collection {
         }
 
         if !decks_needing_memory_recompute.is_empty() {
-            let input: Vec<(Weights, Vec<SearchNode>)> = decks_needing_memory_recompute
+            let input: Vec<(Option<Weights>, Vec<SearchNode>)> = decks_needing_memory_recompute
                 .into_iter()
                 .map(|(conf_id, search)| {
-                    let weights = configs_after_update
-                        .get(&conf_id)
-                        .or_not_found(conf_id)?
-                        .inner
-                        .fsrs_weights
-                        .clone();
+                    let weights = configs_after_update.get(&conf_id).and_then(|c| {
+                        if c.inner.fsrs_enabled {
+                            Some(c.inner.fsrs_weights.clone())
+                        } else {
+                            None
+                        }
+                    });
                     Ok((weights, search))
                 })
                 .collect::<Result<_>>()?;
diff --git a/rslib/src/scheduler/fsrs/memory_state.rs b/rslib/src/scheduler/fsrs/memory_state.rs
index fc8dfac66..bfca1e7ce 100644
--- a/rslib/src/scheduler/fsrs/memory_state.rs
+++ b/rslib/src/scheduler/fsrs/memory_state.rs
@@ -21,9 +21,11 @@ impl Collection {
     /// For each provided set of weights, locate cards with the provided search,
     /// and update their memory state.
     /// Should be called inside a transaction.
+    /// If Weights are None, it means the user disabled FSRS, and the existing
+    /// memory state should be removed.
     pub(crate) fn update_memory_state(
         &mut self,
-        entries: Vec<(Weights, Vec<SearchNode>)>,
+        entries: Vec<(Option<Weights>, Vec<SearchNode>)>,
     ) -> Result<()> {
         let timing = self.timing_today()?;
         let usn = self.usn()?;
@@ -32,15 +34,19 @@ impl Collection {
                 .and(SearchNode::State(StateKind::New).negated());
             let revlog = self.revlog_for_srs(search)?;
             let items = fsrs_items_for_memory_state(revlog, timing.next_day_at);
-            let fsrs = FSRS::new(Some(&weights))?;
+            let fsrs = FSRS::new(weights.as_deref())?;
             let mut progress = self.new_progress_handler::<ComputeMemoryProgress>();
             progress.update(false, |s| s.total_cards = items.len() as u32)?;
             for (idx, (card_id, item)) in items.into_iter().enumerate() {
                 progress.update(true, |state| state.current_cards = idx as u32 + 1)?;
-                let state = fsrs.memory_state(item);
                 let mut card = self.storage.get_card(card_id)?.or_not_found(card_id)?;
                 let original = card.clone();
-                card.memory_state = Some(state.into());
+                if weights.is_some() {
+                    let state = fsrs.memory_state(item);
+                    card.memory_state = Some(state.into());
+                } else {
+                    card.memory_state = None;
+                }
                 self.update_card_inner(&mut card, original, usn)?;
             }
         }