diff --git a/chain/events/events_height.go b/chain/events/events_height.go
index 6ac06de6b..2f93c20f5 100644
--- a/chain/events/events_height.go
+++ b/chain/events/events_height.go
@@ -27,16 +27,34 @@ func (e *heightEvents) headChangeAt(rev, app []*types.TipSet) error {
 		// TODO: log error if h below gcconfidence
 		// revert height-based triggers
 
-		for _, tid := range e.htHeights[ts.Height()] {
-			// don't revert if newH is above this ts
-			if newH >= ts.Height() {
-				continue
+		revert := func(h uint64, ts *types.TipSet) {
+			for _, tid := range e.htHeights[h] {
+				// don't revert if newH is above this ts
+				if newH >= h {
+					continue
+				}
+
+				err := e.heightTriggers[tid].revert(ts)
+				if err != nil {
+					log.Errorf("reverting chain trigger (@H %d): %s", h, err)
+				}
+			}
+		}
+		revert(ts.Height(), ts)
+
+		subh := ts.Height() - 1
+		for {
+			cts, err := e.tsc.get(subh)
+			if err != nil {
+				return err
 			}
 
-			err := e.heightTriggers[tid].revert(ts)
-			if err != nil {
-				log.Errorf("reverting chain trigger (@H %d): %s", ts.Height(), err)
+			if cts != nil {
+				break
 			}
+
+			revert(subh, nil)
+			subh--
 		}
 
 		if err := e.tsc.revert(ts); err != nil {
@@ -54,19 +72,44 @@ func (e *heightEvents) headChangeAt(rev, app []*types.TipSet) error {
 
 		// height triggers
 
-		for _, tid := range e.htTriggerHeights[ts.Height()] {
-			hnd := e.heightTriggers[tid]
-			triggerH := ts.Height() - uint64(hnd.confidence)
+		apply := func(h uint64, ts *types.TipSet) error {
+			for _, tid := range e.htTriggerHeights[h] {
+				hnd := e.heightTriggers[tid]
+				triggerH := h - uint64(hnd.confidence)
 
-			incTs, err := e.tsc.get(triggerH)
+				incTs, err := e.tsc.get(triggerH)
+				if err != nil {
+					return err
+				}
+
+				if err := hnd.handle(incTs, h); err != nil {
+					log.Errorf("chain trigger (@H %d, called @ %d) failed: %s", triggerH, ts.Height(), err)
+				}
+			}
+			return nil
+		}
+
+		if err := apply(ts.Height(), ts); err != nil {
+			return err
+		}
+		subh := ts.Height() - 1
+		for {
+			cts, err := e.tsc.get(subh)
 			if err != nil {
 				return err
 			}
 
-			if err := hnd.handle(incTs, ts.Height()); err != nil {
-				log.Errorf("chain trigger (@H %d, called @ %d) failed: %s", triggerH, ts.Height(), err)
+			if cts != nil {
+				break
 			}
+
+			if err := apply(subh, nil); err != nil {
+				return err
+			}
+
+			subh--
 		}
+
 	}
 
 	return nil
diff --git a/chain/events/events_test.go b/chain/events/events_test.go
index 9d267d67c..3a7874489 100644
--- a/chain/events/events_test.go
+++ b/chain/events/events_test.go
@@ -114,21 +114,28 @@ func (fcs *fakeCS) fakeMsgs(m fakeMsg) cid.Cid {
 	return c
 }
 
-func (fcs *fakeCS) advance(rev, app int, msgs map[int]cid.Cid) { // todo: allow msgs
+func (fcs *fakeCS) advance(rev, app int, msgs map[int]cid.Cid, nulls ...int) { // todo: allow msgs
 	if fcs.sub == nil {
 		fcs.t.Fatal("sub not be nil")
 	}
 
+	nullm := map[int]struct{}{}
+	for _, v := range nulls {
+		nullm[v] = struct{}{}
+	}
+
 	var revs []*types.TipSet
 	for i := 0; i < rev; i++ {
 		ts := fcs.tsc.best()
 
-		revs = append(revs, ts)
+		if _, ok := nullm[int(ts.Height())]; !ok {
+			revs = append(revs, ts)
+			require.NoError(fcs.t, fcs.tsc.revert(ts))
+		}
 		fcs.h--
-		require.NoError(fcs.t, fcs.tsc.revert(ts))
 	}
 
-	apps := make([]*types.TipSet, app)
+	var apps []*types.TipSet
 	for i := 0; i < app; i++ {
 		fcs.h++
 
@@ -137,6 +144,10 @@ func (fcs *fakeCS) advance(rev, app int, msgs map[int]cid.Cid) { // todo: allow
 			mc = dummyCid
 		}
 
+		if _, ok := nullm[int(fcs.h)]; ok {
+			continue
+		}
+
 		ts := makeTs(fcs.t, fcs.h, mc)
 		require.NoError(fcs.t, fcs.tsc.add(ts))
 
@@ -144,7 +155,11 @@ func (fcs *fakeCS) advance(rev, app int, msgs map[int]cid.Cid) { // todo: allow
 			fcs.blkMsgs[ts.Blocks()[0].Cid()] = mc
 		}
 
-		apps[app-i-1] = ts
+		apps = append(apps, ts)
+	}
+
+	for i, j := 0, len(apps)-1; i < j; i, j = i+1, j-1 {
+		apps[i], apps[j] = apps[j], apps[i]
 	}
 
 	fcs.sub(revs, apps)
@@ -212,6 +227,79 @@ func TestAt(t *testing.T) {
 	require.Equal(t, false, reverted)
 }
 
+func TestAtNullTrigger(t *testing.T) {
+	fcs := &fakeCS{
+		t:   t,
+		h:   1,
+		tsc: newTSCache(2*build.ForkLengthThreshold, nil),
+	}
+	require.NoError(t, fcs.tsc.add(makeTs(t, 1, dummyCid)))
+
+	events := NewEvents(context.Background(), fcs)
+
+	var applied bool
+	var reverted bool
+
+	err := events.ChainAt(func(ts *types.TipSet, curH uint64) error {
+		require.Nil(t, ts)
+		require.Equal(t, 8, int(curH))
+		applied = true
+		return nil
+	}, func(ts *types.TipSet) error {
+		reverted = true
+		return nil
+	}, 3, 5)
+	require.NoError(t, err)
+
+	fcs.advance(0, 6, nil, 5)
+	require.Equal(t, false, applied)
+	require.Equal(t, false, reverted)
+
+	fcs.advance(0, 3, nil)
+	require.Equal(t, true, applied)
+	require.Equal(t, false, reverted)
+	applied = false
+}
+
+func TestAtNullConf(t *testing.T) {
+	fcs := &fakeCS{
+		t:   t,
+		h:   1,
+		tsc: newTSCache(2*build.ForkLengthThreshold, nil),
+	}
+	require.NoError(t, fcs.tsc.add(makeTs(t, 1, dummyCid)))
+
+	events := NewEvents(context.Background(), fcs)
+
+	var applied bool
+	var reverted bool
+
+	err := events.ChainAt(func(ts *types.TipSet, curH uint64) error {
+		require.Equal(t, 5, int(ts.Height()))
+		require.Equal(t, 8, int(curH))
+		applied = true
+		return nil
+	}, func(ts *types.TipSet) error {
+		reverted = true
+		return nil
+	}, 3, 5)
+	require.NoError(t, err)
+
+	fcs.advance(0, 6, nil)
+	require.Equal(t, false, applied)
+	require.Equal(t, false, reverted)
+
+	fcs.advance(0, 3, nil, 8)
+	require.Equal(t, true, applied)
+	require.Equal(t, false, reverted)
+	applied = false
+
+	fcs.advance(7, 1, nil)
+	require.Equal(t, false, applied)
+	require.Equal(t, true, reverted)
+	reverted = false
+}
+
 func TestAtStart(t *testing.T) {
 	fcs := &fakeCS{
 		t:   t,
diff --git a/chain/events/tscache.go b/chain/events/tscache.go
index 9cbd0587c..c1fc338cd 100644
--- a/chain/events/tscache.go
+++ b/chain/events/tscache.go
@@ -31,11 +31,26 @@ func newTSCache(cap int, storage tsByHFunc) *tipSetCache {
 
 func (tsc *tipSetCache) add(ts *types.TipSet) error {
 	if tsc.len > 0 {
-		if tsc.cache[tsc.start].Height()+1 != ts.Height() {
-			return xerrors.Errorf("tipSetCache.add: expected new tipset height to be %d, was %d", tsc.cache[tsc.start].Height()+1, ts.Height())
+		if tsc.cache[tsc.start].Height() >= ts.Height() {
+			return xerrors.Errorf("tipSetCache.add: expected new tipset height to be at least %d, was %d", tsc.cache[tsc.start].Height()+1, ts.Height())
 		}
 	}
 
+	nextH := ts.Height()
+	if tsc.len > 0 {
+		nextH = tsc.cache[tsc.start].Height() + 1
+	}
+
+	// fill null blocks
+	for nextH != ts.Height() {
+		tsc.start = normalModulo(tsc.start+1, len(tsc.cache))
+		tsc.cache[tsc.start] = nil
+		if tsc.len < len(tsc.cache) {
+			tsc.len++
+		}
+		nextH++
+	}
+
 	tsc.start = normalModulo(tsc.start+1, len(tsc.cache))
 	tsc.cache[tsc.start] = ts
 	if tsc.len < len(tsc.cache) {
@@ -56,6 +71,8 @@ func (tsc *tipSetCache) revert(ts *types.TipSet) error {
 	tsc.cache[tsc.start] = nil
 	tsc.start = normalModulo(tsc.start-1, len(tsc.cache))
 	tsc.len--
+
+	_ = tsc.revert(nil) // revert null block gap
 	return nil
 }
 
diff --git a/chain/events/tscache_test.go b/chain/events/tscache_test.go
index beedfe8da..45c1a23eb 100644
--- a/chain/events/tscache_test.go
+++ b/chain/events/tscache_test.go
@@ -2,7 +2,7 @@ package events
 
 import (
 	"context"
-	"fmt"
+	"github.com/stretchr/testify/require"
 	"testing"
 
 	"github.com/filecoin-project/go-lotus/chain/types"
@@ -33,8 +33,6 @@ func TestTsCache(t *testing.T) {
 	}
 
 	for i := 0; i < 9000; i++ {
-		fmt.Printf("i=%d; tl=%d; tcl=%d\n", i, tsc.len, len(tsc.cache))
-
 		if i%90 > 60 {
 			if err := tsc.revert(tsc.best()); err != nil {
 				t.Fatal(err, "; i:", i)
@@ -47,3 +45,58 @@ func TestTsCache(t *testing.T) {
 	}
 
 }
+
+func TestTsCacheNulls(t *testing.T) {
+	tsc := newTSCache(50, func(context.Context, uint64, *types.TipSet) (*types.TipSet, error) {
+		t.Fatal("storage call")
+		return &types.TipSet{}, nil
+	})
+
+	h := uint64(75)
+
+	add := func() {
+		ts, err := types.NewTipSet([]*types.BlockHeader{{
+			Height:                h,
+			ParentStateRoot:       dummyCid,
+			Messages:              dummyCid,
+			ParentMessageReceipts: dummyCid,
+		}})
+		if err != nil {
+			t.Fatal(err)
+		}
+		if err := tsc.add(ts); err != nil {
+			t.Fatal(err)
+		}
+		h++
+	}
+
+	add()
+	add()
+	add()
+	h += 5
+
+	add()
+	add()
+
+	require.Equal(t, h-1, tsc.best().Height())
+
+	ts, err := tsc.get(h - 1)
+	require.NoError(t, err)
+	require.Equal(t, h-1, ts.Height())
+
+	ts, err = tsc.get(h - 2)
+	require.NoError(t, err)
+	require.Equal(t, h-2, ts.Height())
+
+	ts, err = tsc.get(h - 3)
+	require.NoError(t, err)
+	require.Nil(t, ts)
+
+	ts, err = tsc.get(h - 8)
+	require.NoError(t, err)
+	require.Equal(t, h-8, ts.Height())
+
+	require.NoError(t, tsc.revert(tsc.best()))
+	require.NoError(t, tsc.revert(tsc.best()))
+	require.Equal(t, h-8, tsc.best().Height())
+}
diff --git a/chain/types/tipset.go b/chain/types/tipset.go
index 688edacd4..990cbf5cb 100644
--- a/chain/types/tipset.go
+++ b/chain/types/tipset.go
@@ -104,6 +104,13 @@ func (ts *TipSet) Blocks() []*BlockHeader {
 }
 
 func (ts *TipSet) Equals(ots *TipSet) bool {
+	if ts == nil && ots == nil {
+		return true
+	}
+	if ts == nil || ots == nil {
+		return false
+	}
+
 	if len(ts.blks) != len(ots.blks) {
 		return false
 	}
diff --git a/cmd/lotus-fountain/main.go b/cmd/lotus-fountain/main.go
index 8b8a457fd..f6f8d91fb 100644
--- a/cmd/lotus-fountain/main.go
+++ b/cmd/lotus-fountain/main.go
@@ -64,7 +64,7 @@ var runCmd = &cli.Command{
 		},
 	},
 	Action: func(cctx *cli.Context) error {
-		nodeApi, closer,  err := lcli.GetFullNodeAPI(cctx)
+		nodeApi, closer, err := lcli.GetFullNodeAPI(cctx)
 		if err != nil {
 			return err
 		}