diff --git a/CHANGELOG.md b/CHANGELOG.md
index ef0e0142166..99a3b4d1b94 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,6 +3,7 @@
 # UNRELEASED
 
 - Add Market PendingProposals API / CLI. ([filecoin-project/lotus#12724](https://github.com/filecoin-project/lotus/pull/12724))
+- Fix checkpointed tipsets being expanded #12747
 
 ## Improvements
 
diff --git a/chain/sync.go b/chain/sync.go
index bfc2d01214d..7f1aebf03ab 100644
--- a/chain/sync.go
+++ b/chain/sync.go
@@ -845,6 +845,14 @@ loop:
 	if err != nil {
 		return nil, xerrors.Errorf("failed to load next local tipset: %w", err)
 	}
+
+	if chkpt := syncer.store.GetCheckpoint(); !ignoreCheckpoint && chkpt != nil {
+		// don't allow us to expand the tipset beyond the checkpoint
+		if known.Equals(chkpt) && base.IsChildOf(knownParent) {
+			return nil, xerrors.Errorf("tispet expanding fork: %w", ErrForkCheckpoint)
+		}
+	}
+
 	if base.IsChildOf(knownParent) {
 		// common case: receiving a block that's potentially part of the same tipset as our best block
 		return blockSet, nil
diff --git a/chain/sync_test.go b/chain/sync_test.go
index 4cff5767ed5..a2d7175572a 100644
--- a/chain/sync_test.go
+++ b/chain/sync_test.go
@@ -110,7 +110,7 @@ func prepSyncTest(t testing.TB, h int) *syncTestUtil {
 	//tu.checkHeight("source", source, h)
 
 	// separate logs
-	fmt.Println("\x1b[31m///////////////////////////////////////////////////\x1b[39b")
+	fmt.Println("///////////////////////////////////////////////////")
 
 	return tu
 }
@@ -175,7 +175,7 @@ func prepSyncTestWithV5Height(t testing.TB, h int, v5height abi.ChainEpoch) *syn
 	//tu.checkHeight("source", source, h)
 
 	// separate logs
-	fmt.Println("\x1b[31m///////////////////////////////////////////////////\x1b[39b")
+	fmt.Println("///////////////////////////////////////////////////")
 	return tu
 }
 
@@ -208,6 +208,7 @@ func (tu *syncTestUtil) pushFtsAndWait(to int, fts *store.FullTipSet, wait bool)
 			require.NoError(tu.t, err)
 
 			if time.Since(start) > time.Second*10 {
+				tu.t.Helper()
 				tu.t.Fatal("took too long waiting for block to be accepted")
 			}
 		}
@@ -219,7 +220,6 @@ func (tu *syncTestUtil) pushTsExpectErr(to int, fts *store.FullTipSet, experr bo
 	for _, fb := range fts.Blocks {
 		var b types.BlockMsg
 
-		// -1 to match block.Height
 		b.Header = fb.Header
 		for _, msg := range fb.SecpkMessages {
 			c, err := tu.nds[to].(*impl.FullNodeAPI).ChainAPI.Chain.PutMessage(ctx, msg)
@@ -1026,6 +1026,64 @@ func TestSyncCheckpointHead(t *testing.T) {
 	require.True(tu.t, p1Head.Equals(b.TipSet()))
 }
 
+func TestSyncCheckpointPartial(t *testing.T) {
+	H := 10
+	tu := prepSyncTest(t, H)
+
+	p1 := tu.addClientNode()
+	p2 := tu.addClientNode()
+
+	fmt.Println("GENESIS: ", tu.g.Genesis().Cid())
+	tu.loadChainToNode(p1)
+	tu.loadChainToNode(p2)
+
+	base := tu.g.CurTipset
+	fmt.Println("Mining base: ", base.TipSet().Cids(), base.TipSet().Height())
+
+	last := base
+	a := base
+	for {
+		a = tu.mineOnBlock(last, p1, []int{0, 1}, true, false, nil, 0, true)
+		if len(a.Blocks) == 2 {
+			// enfoce tipset of two blocks
+			break
+		}
+		tu.pushTsExpectErr(p2, a, false) // push these to p2 as well
+		last = a
+	}
+	var aPartial *store.FullTipSet
+	var aPartial2 *store.FullTipSet
+	for _, b := range a.Blocks {
+		if b.Header.Miner == tu.g.Miners[1] {
+			// need to have miner two block in the partial tipset
+			// as otherwise it will be a parent grinding fault
+			aPartial = store.NewFullTipSet([]*types.FullBlock{b})
+		} else {
+			aPartial2 = store.NewFullTipSet([]*types.FullBlock{b})
+		}
+	}
+	tu.waitUntilSyncTarget(p1, a.TipSet())
+
+	tu.pushFtsAndWait(p2, aPartial, true)
+	tu.checkpointTs(p2, aPartial.TipSet().Key())
+	t.Logf("p1 head: %v, p2 head: %v, a: %v", tu.getHead(p1), tu.getHead(p2), a.TipSet())
+	tu.pushTsExpectErr(p2, aPartial2, true)
+
+	b := tu.mineOnBlock(a, p1, []int{0}, true, false, nil, 0, true)
+	tu.pushTsExpectErr(p2, b, true)
+
+	require.NoError(t, tu.g.ResyncBankerNonce(b.TipSet())) // don't ask me why it has to be TS b
+	c := tu.mineOnBlock(aPartial, p2, []int{1}, true, false, nil, 0, true)
+
+	require.NoError(t, tu.mn.LinkAll())
+	tu.connect(p1, p2)
+
+	tu.pushFtsAndWait(p2, c, true)
+	tu.waitUntilNodeHasTs(p1, c.TipSet().Key())
+	tu.checkpointTs(p1, c.TipSet().Key())
+
+}
+
 func TestSyncCheckpointEarlierThanHead(t *testing.T) {
 	//stm: @BLOCKCHAIN_BEACON_VALIDATE_BLOCK_VALUES_01, @CHAIN_SYNCER_LOAD_GENESIS_001, @CHAIN_SYNCER_FETCH_TIPSET_001, @CHAIN_SYNCER_START_001
 	//stm: @CHAIN_SYNCER_SYNC_001, @CHAIN_SYNCER_COLLECT_CHAIN_001, @CHAIN_SYNCER_COLLECT_HEADERS_001