diff --git a/rslib/src/stats/card.rs b/rslib/src/stats/card.rs
index 48fdc3457..6971311bf 100644
--- a/rslib/src/stats/card.rs
+++ b/rslib/src/stats/card.rs
@@ -152,14 +152,23 @@ impl Collection {
             let mut revlog_index = 0;
             for entry in revlog {
                 let mut stats_entry = stats_revlog_entry(&entry);
-                let memory_state: FsrsMemoryState =
-                    if entry.id == item.filtered_revlogs[revlog_index].id {
-                        revlog_index += 1;
-                        memory_states[revlog_index - 1].into()
-                    } else {
-                        memory_states[revlog_index].into()
-                    };
-                stats_entry.memory_state = Some(memory_state.into());
+                let memory_state: Option<FsrsMemoryState> = if revlog_index >= memory_states.len() {
+                    // The removed revlog is in the end of the revlog, so we use the last memory
+                    // state
+                    Some(memory_states[memory_states.len() - 1].into())
+                } else if entry.id == item.filtered_revlogs[revlog_index].id {
+                    revlog_index += 1;
+                    Some(memory_states[revlog_index - 1].into())
+                } else if revlog_index == 0 {
+                    // The removed revlog is in the start of the revlog, so we don't have a memory
+                    // state for it
+                    None
+                } else {
+                    // The removed revlog is in the middle of the revlog, so we use the memory
+                    // state for the previous revlog entry
+                    Some(memory_states[revlog_index].into())
+                };
+                stats_entry.memory_state = memory_state.map(|s| s.into());
                 result.push(stats_entry);
             }
             Ok(result.into_iter().rev().collect())
diff --git a/ts/routes/card-info/forgetting-curve.ts b/ts/routes/card-info/forgetting-curve.ts
index cb9dc2962..9f0301fce 100644
--- a/ts/routes/card-info/forgetting-curve.ts
+++ b/ts/routes/card-info/forgetting-curve.ts
@@ -56,7 +56,10 @@ export function filterRevlogEntryByReviewKind(entry: RevlogEntry): boolean {
 export function filterRevlog(revlog: RevlogEntry[]): RevlogEntry[] {
     const result: RevlogEntry[] = [];
     for (const entry of revlog) {
-        if (entry.reviewKind === RevlogEntry_ReviewKind.MANUAL && entry.ease === 0) {
+        if (
+            (entry.reviewKind === RevlogEntry_ReviewKind.MANUAL && entry.ease === 0)
+            || entry.memoryState === undefined
+        ) {
             break;
         }
         result.push(entry);