diff --git a/proto/anki/scheduler.proto b/proto/anki/scheduler.proto
index 01f092a39..1294b4543 100644
--- a/proto/anki/scheduler.proto
+++ b/proto/anki/scheduler.proto
@@ -404,6 +404,7 @@ message SimulateFsrsReviewRequest {
   repeated float easy_days_percentages = 10;
   deck_config.DeckConfig.Config.ReviewCardOrder review_order = 11;
   optional uint32 suspend_after_lapse_count = 12;
+  float historical_retention = 13;
 }
 
 message SimulateFsrsReviewResponse {
diff --git a/rslib/src/scheduler/fsrs/simulator.rs b/rslib/src/scheduler/fsrs/simulator.rs
index 2d43cc4a7..4e0907eb3 100644
--- a/rslib/src/scheduler/fsrs/simulator.rs
+++ b/rslib/src/scheduler/fsrs/simulator.rs
@@ -146,7 +146,6 @@ impl Collection {
         let new_cards =
             cards.iter().filter(|c| c.queue == CardQueue::New).count() + req.deck_size as usize;
         let fsrs = FSRS::new(Some(&req.params))?;
-        let historical_retention = req.desired_retention;
         let mut converted_cards = cards
             .into_iter()
             .filter(is_included_card)
@@ -157,7 +156,7 @@ impl Collection {
                         .memory_state_from_sm2(
                             c.ease_factor(),
                             c.interval as f32,
-                            historical_retention,
+                            req.historical_retention,
                         )
                         .ok()?
                         .into(),
diff --git a/ts/routes/deck-options/FsrsOptions.svelte b/ts/routes/deck-options/FsrsOptions.svelte
index 706407889..cfdea341c 100644
--- a/ts/routes/deck-options/FsrsOptions.svelte
+++ b/ts/routes/deck-options/FsrsOptions.svelte
@@ -95,6 +95,7 @@ License: GNU AGPL, version 3 or later; http://www.gnu.org/licenses/agpl.html
         newCardsIgnoreReviewLimit: $newCardsIgnoreReviewLimit,
         easyDaysPercentages: $config.easyDaysPercentages,
         reviewOrder: $config.reviewOrder,
+        historicalRetention: $config.historicalRetention,
     });
 
     const DESIRED_RETENTION_LOW_THRESHOLD = 0.8;