diff --git a/chia/_tests/core/mempool/test_mempool_manager.py b/chia/_tests/core/mempool/test_mempool_manager.py
index e248a555fc15..b6d38d555340 100644
--- a/chia/_tests/core/mempool/test_mempool_manager.py
+++ b/chia/_tests/core/mempool/test_mempool_manager.py
@@ -3201,3 +3201,61 @@ async def test_new_peak_deferred_ff_items() -> None:
     latest_singleton_lineage2 = mi2.bundle_coin_spends[singleton2_id].latest_singleton_lineage
     assert latest_singleton_lineage2 is not None
     assert latest_singleton_lineage2.coin_id == singleton2_new_latest.name()
+
+
+@pytest.mark.anyio
+async def test_different_ff_versions() -> None:
+    """
+    Covers the case where we send an item with an older ff singleton version
+    while the mempool is aware of a newer lineage.
+    """
+    launcher_id = bytes32([1] * 32)
+    singleton_spend1 = make_singleton_spend(launcher_id, bytes32([2] * 32))
+    version1_id = singleton_spend1.coin.name()
+    singleton_spend2 = make_singleton_spend(launcher_id, bytes32([3] * 32))
+    version2_id = singleton_spend2.coin.name()
+    singleton_ph = singleton_spend2.coin.puzzle_hash
+    coins = TestCoins(
+        [singleton_spend1.coin, singleton_spend2.coin, TEST_COIN, TEST_COIN2], {singleton_ph: singleton_spend2.coin}
+    )
+    mempool_manager = await setup_mempool(coins)
+    mempool_items: list[MempoolItem] = []
+    for singleton_spend, regular_coin in [(singleton_spend1, TEST_COIN), (singleton_spend2, TEST_COIN2)]:
+        sb = SpendBundle([singleton_spend, mk_coin_spend(regular_coin)], G2Element())
+        sb_name = sb.name()
+        await mempool_manager.add_spend_bundle(
+            sb,
+            make_test_conds(spend_ids=[(singleton_spend.coin, ELIGIBLE_FOR_FF), (regular_coin, 0)], cost=1337),
+            sb_name,
+            uint32(1),
+        )
+        mi = mempool_manager.get_mempool_item(sb_name)
+        assert mi is not None
+        mempool_items.append(mi)
+    [mi1, mi2] = mempool_items
+    latest_lineage_id = version2_id
+    assert latest_lineage_id != version1_id
+    # Bundle coin spends key points to version 1 but the lineage is latest (v2)
+    latest_singleton_lineage1 = mi1.bundle_coin_spends[version1_id].latest_singleton_lineage
+    assert latest_singleton_lineage1 is not None
+    assert latest_singleton_lineage1.coin_id == latest_lineage_id
+    # Both the bundle coin spends key and the lineage point to latest (v2)
+    latest_singleton_lineage2 = mi2.bundle_coin_spends[version2_id].latest_singleton_lineage
+    assert latest_singleton_lineage2 is not None
+    assert latest_singleton_lineage2.coin_id == latest_lineage_id
+    # Let's update the lineage with a new version of the singleton
+    new_latest_lineage = Coin(version2_id, singleton_ph, singleton_spend2.coin.amount)
+    new_latest_lineage_id = new_latest_lineage.name()
+    coins.update_lineage(singleton_ph, new_latest_lineage)
+    await advance_mempool(mempool_manager, [version1_id, version2_id], use_optimization=True)
+    # Both items should get updated with the latest lineage
+    new_mi1 = mempool_manager.get_mempool_item(mi1.spend_bundle_name)
+    assert new_mi1 is not None
+    latest_singleton_lineage1 = new_mi1.bundle_coin_spends[version1_id].latest_singleton_lineage
+    assert latest_singleton_lineage1 is not None
+    assert latest_singleton_lineage1.coin_id == new_latest_lineage_id
+    new_mi2 = mempool_manager.get_mempool_item(mi2.spend_bundle_name)
+    assert new_mi2 is not None
+    latest_singleton_lineage2 = new_mi2.bundle_coin_spends[version2_id].latest_singleton_lineage
+    assert latest_singleton_lineage2 is not None
+    assert latest_singleton_lineage2.coin_id == new_latest_lineage_id
diff --git a/chia/full_node/mempool_manager.py b/chia/full_node/mempool_manager.py
index ced16a747639..a13f0e727310 100644
--- a/chia/full_node/mempool_manager.py
+++ b/chia/full_node/mempool_manager.py
@@ -257,7 +257,22 @@ def check_removals(
         for item in conflicting_items:
             if item in conflicts:
                 continue
-            conflict_bcs = item.bundle_coin_spends[coin_id]
+            conflict_bcs = item.bundle_coin_spends.get(coin_id)
+            if conflict_bcs is None:
+                # Check if this is an item that spends an older ff singleton
+                # version with a latest version that matches our coin ID.
+                conflict_bcs = next(
+                    (
+                        bcs
+                        for bcs in item.bundle_coin_spends.values()
+                        if bcs.latest_singleton_lineage is not None and bcs.latest_singleton_lineage.coin_id == coin_id
+                    ),
+                    None,
+                )
+                # We're not expected to get here but let's handle it gracefully
+                if conflict_bcs is None:
+                    log.warning(f"Coin ID {coin_id} expected but not found in mempool item {item.name}")
+                    return Err.INVALID_SPEND_BUNDLE, []
             # if the spend we're adding to the mempool is not DEDUP nor FF, it's
             # just a regular conflict
             if not coin_bcs.eligible_for_fast_forward and not coin_bcs.eligible_for_dedup: