diff --git a/api/api_full.go b/api/api_full.go
index 7ebc8791a..1311dac6a 100644
--- a/api/api_full.go
+++ b/api/api_full.go
@@ -172,6 +172,9 @@ type FullNode interface {
 	// SyncUnmarkBad unmarks a blocks as bad, making it possible to be validated and synced again.
 	SyncUnmarkBad(ctx context.Context, bcid cid.Cid) error
 
+	// SyncUnmarkAllBad purges bad block cache, making it possible to sync to chains previously marked as bad
+	SyncUnmarkAllBad(ctx context.Context) error
+
 	// SyncCheckBad checks if a block was marked as bad, and if it was, returns
 	// the reason.
 	SyncCheckBad(ctx context.Context, bcid cid.Cid) (string, error)
diff --git a/api/apistruct/struct.go b/api/apistruct/struct.go
index 348e8a6de..6bfbf43cb 100644
--- a/api/apistruct/struct.go
+++ b/api/apistruct/struct.go
@@ -111,6 +111,7 @@ type FullNodeStruct struct {
 		SyncCheckpoint     func(ctx context.Context, key types.TipSetKey) error         `perm:"admin"`
 		SyncMarkBad        func(ctx context.Context, bcid cid.Cid) error                `perm:"admin"`
 		SyncUnmarkBad      func(ctx context.Context, bcid cid.Cid) error                `perm:"admin"`
+		SyncUnmarkAllBad   func(ctx context.Context) error                `perm:"admin"`
 		SyncCheckBad       func(ctx context.Context, bcid cid.Cid) (string, error)      `perm:"read"`
 		SyncValidateTipset func(ctx context.Context, tsk types.TipSetKey) (bool, error) `perm:"read"`
 
@@ -780,6 +781,10 @@ func (c *FullNodeStruct) SyncUnmarkBad(ctx context.Context, bcid cid.Cid) error
 	return c.Internal.SyncUnmarkBad(ctx, bcid)
 }
 
+func (c *FullNodeStruct) SyncUnmarkAllBad(ctx context.Context) error {
+	return c.Internal.SyncUnmarkAllBad(ctx)
+}
+
 func (c *FullNodeStruct) SyncCheckBad(ctx context.Context, bcid cid.Cid) (string, error) {
 	return c.Internal.SyncCheckBad(ctx, bcid)
 }
diff --git a/chain/badtscache.go b/chain/badtscache.go
index 3c5bf05ef..42564128e 100644
--- a/chain/badtscache.go
+++ b/chain/badtscache.go
@@ -60,6 +60,10 @@ func (bts *BadBlockCache) Remove(c cid.Cid) {
 	bts.badBlocks.Remove(c)
 }
 
+func (bts *BadBlockCache) Purge() {
+	bts.badBlocks.Purge()
+}
+
 func (bts *BadBlockCache) Has(c cid.Cid) (BadBlockReason, bool) {
 	rval, ok := bts.badBlocks.Get(c)
 	if !ok {
diff --git a/chain/sync.go b/chain/sync.go
index 369c65d33..23688ecb7 100644
--- a/chain/sync.go
+++ b/chain/sync.go
@@ -1740,6 +1740,10 @@ func (syncer *Syncer) UnmarkBad(blk cid.Cid) {
 	syncer.bad.Remove(blk)
 }
 
+func (syncer *Syncer) UnmarkAllBad() {
+	syncer.bad.Purge()
+}
+
 func (syncer *Syncer) CheckBadBlockCache(blk cid.Cid) (string, bool) {
 	bbr, ok := syncer.bad.Has(blk)
 	return bbr.String(), ok
diff --git a/cli/sync.go b/cli/sync.go
index dea96d14e..a5178441d 100644
--- a/cli/sync.go
+++ b/cli/sync.go
@@ -124,6 +124,12 @@ var syncMarkBadCmd = &cli.Command{
 var syncUnmarkBadCmd = &cli.Command{
 	Name:      "unmark-bad",
 	Usage:     "Unmark the given block as bad, makes it possible to sync to a chain containing it",
+	Flags: []cli.Flag{
+		&cli.BoolFlag{
+			Name: "all",
+			Usage: "drop the entire bad block cache",
+		},
+	},
 	ArgsUsage: "[blockCid]",
 	Action: func(cctx *cli.Context) error {
 		napi, closer, err := GetFullNodeAPI(cctx)
@@ -133,6 +139,10 @@ var syncUnmarkBadCmd = &cli.Command{
 		defer closer()
 		ctx := ReqContext(cctx)
 
+		if cctx.Bool("all") {
+			return napi.SyncUnmarkAllBad(ctx)
+		}
+
 		if !cctx.Args().Present() {
 			return fmt.Errorf("must specify block cid to unmark")
 		}
diff --git a/node/impl/full/sync.go b/node/impl/full/sync.go
index 1bd3af415..05d4c9cb7 100644
--- a/node/impl/full/sync.go
+++ b/node/impl/full/sync.go
@@ -118,6 +118,12 @@ func (a *SyncAPI) SyncUnmarkBad(ctx context.Context, bcid cid.Cid) error {
 	return nil
 }
 
+func (a *SyncAPI) SyncUnmarkAllBad(ctx context.Context) error {
+	log.Warnf("Dropping bad block cache")
+	a.Syncer.UnmarkAllBad()
+	return nil
+}
+
 func (a *SyncAPI) SyncCheckBad(ctx context.Context, bcid cid.Cid) (string, error) {
 	reason, ok := a.Syncer.CheckBadBlockCache(bcid)
 	if !ok {