diff --git a/accounts-db/src/accounts_index/in_mem_accounts_index.rs b/accounts-db/src/accounts_index/in_mem_accounts_index.rs
index 7d7a810afb06d8..5bd40a695ff327 100644
--- a/accounts-db/src/accounts_index/in_mem_accounts_index.rs
+++ b/accounts-db/src/accounts_index/in_mem_accounts_index.rs
@@ -769,13 +769,25 @@ impl<T: IndexValue, U: DiskIndexValue + From<T> + Into<T>> InMemAccountsIndex<T,
                 }
                 drop(slot_list);
 
-                InMemAccountsIndex::<T, U>::lock_and_update_slot_list(
+                let updated_slot_list_len = InMemAccountsIndex::<T, U>::lock_and_update_slot_list(
                     occupied.get(),
                     (slot, account_info),
                     None, // should be None because we don't expect a different slot # during index generation
                     &mut Vec::default(),
                     UpsertReclaim::IgnoreReclaims,
                 );
+
+                // In case of a race condition, multiple threads try to insert
+                // to the same pubkey with different slots. We only need to
+                // record `other_slot` once. If the slot list length after
+                // update is not 2, it means that someone else has already
+                // recorded `other_slot` before us. Therefore, We don't need to
+                // record it again.
+                if updated_slot_list_len != 2 {
+                    // clear `other_slot` if we don't win the race.
+                    other_slot = None;
+                }
+
                 (
                     true, /* found in mem */
                     true, /* already existed */