diff --git a/chain/gen/gen.go b/chain/gen/gen.go
index ebf868765..54040deb4 100644
--- a/chain/gen/gen.go
+++ b/chain/gen/gen.go
@@ -145,7 +145,7 @@ func NewGeneratorWithSectors(numSectors int) (*ChainGen, error) {
 		return nil, err
 	}
 
-	genm1, k1, err := seed.PreSeal(maddr1, abi.RegisteredSealProof_StackedDrg2KiBV1, 0, numSectors, m1temp, []byte("some randomness"), nil)
+	genm1, k1, err := seed.PreSeal(maddr1, abi.RegisteredSealProof_StackedDrg2KiBV1, 0, numSectors, m1temp, []byte("some randomness"), nil, true)
 	if err != nil {
 		return nil, err
 	}
@@ -157,7 +157,7 @@ func NewGeneratorWithSectors(numSectors int) (*ChainGen, error) {
 		return nil, err
 	}
 
-	genm2, k2, err := seed.PreSeal(maddr2, abi.RegisteredSealProof_StackedDrg2KiBV1, 0, numSectors, m2temp, []byte("some randomness"), nil)
+	genm2, k2, err := seed.PreSeal(maddr2, abi.RegisteredSealProof_StackedDrg2KiBV1, 0, numSectors, m2temp, []byte("some randomness"), nil, true)
 	if err != nil {
 		return nil, err
 	}
diff --git a/cmd/lotus-seed/main.go b/cmd/lotus-seed/main.go
index 1e4f8fe0d..827c0f112 100644
--- a/cmd/lotus-seed/main.go
+++ b/cmd/lotus-seed/main.go
@@ -89,6 +89,10 @@ var preSealCmd = &cli.Command{
 			Value: "",
 			Usage: "(optional) Key to use for signing / owner/worker addresses",
 		},
+		&cli.BoolFlag{
+			Name: "fake-sectors",
+			Value: false,
+		},
 	},
 	Action: func(c *cli.Context) error {
 		sdir := c.String("sector-dir")
@@ -126,7 +130,7 @@ var preSealCmd = &cli.Command{
 			return err
 		}
 
-		gm, key, err := seed.PreSeal(maddr, rp, abi.SectorNumber(c.Uint64("sector-offset")), c.Int("num-sectors"), sbroot, []byte(c.String("ticket-preimage")), k)
+		gm, key, err := seed.PreSeal(maddr, rp, abi.SectorNumber(c.Uint64("sector-offset")), c.Int("num-sectors"), sbroot, []byte(c.String("ticket-preimage")), k, c.Bool("fake-sectors"))
 		if err != nil {
 			return err
 		}
diff --git a/cmd/lotus-seed/seed/seed.go b/cmd/lotus-seed/seed/seed.go
index 08ae91200..1d6c3da29 100644
--- a/cmd/lotus-seed/seed/seed.go
+++ b/cmd/lotus-seed/seed/seed.go
@@ -17,7 +17,9 @@ import (
 	"github.com/minio/blake2b-simd"
 	"golang.org/x/xerrors"
 
+	ffi "github.com/filecoin-project/filecoin-ffi"
 	"github.com/filecoin-project/go-address"
+	"github.com/filecoin-project/sector-storage/zerocomm"
 	"github.com/filecoin-project/specs-actors/actors/abi"
 	"github.com/filecoin-project/specs-actors/actors/abi/big"
 	"github.com/filecoin-project/specs-actors/actors/builtin/market"
@@ -33,7 +35,7 @@ import (
 
 var log = logging.Logger("preseal")
 
-func PreSeal(maddr address.Address, spt abi.RegisteredSealProof, offset abi.SectorNumber, sectors int, sbroot string, preimage []byte, key *types.KeyInfo) (*genesis.Miner, *types.KeyInfo, error) {
+func PreSeal(maddr address.Address, spt abi.RegisteredSealProof, offset abi.SectorNumber, sectors int, sbroot string, preimage []byte, key *types.KeyInfo, fakeSectors bool) (*genesis.Miner, *types.KeyInfo, error) {
 	mid, err := address.IDFromAddress(maddr)
 	if err != nil {
 		return nil, nil, err
@@ -68,41 +70,20 @@ func PreSeal(maddr address.Address, spt abi.RegisteredSealProof, offset abi.Sect
 		sid := abi.SectorID{Miner: abi.ActorID(mid), Number: next}
 		next++
 
-		pi, err := sb.AddPiece(context.TODO(), sid, nil, abi.PaddedPieceSize(ssize).Unpadded(), rand.Reader)
-		if err != nil {
-			return nil, nil, err
+		var preseal *genesis.PreSeal
+		if !fakeSectors {
+			preseal, err = presealSector(sb, sbfs, sid, spt, ssize, preimage)
+			if err != nil {
+				return nil, nil, err
+			}
+		} else {
+			preseal, err = presealSectorFake(sbfs, sid, spt, ssize)
+			if err != nil {
+				return nil, nil, err
+			}
 		}
 
-		trand := blake2b.Sum256(preimage)
-		ticket := abi.SealRandomness(trand[:])
-
-		fmt.Printf("sector-id: %d, piece info: %v\n", sid, pi)
-
-		in2, err := sb.SealPreCommit1(context.TODO(), sid, ticket, []abi.PieceInfo{pi})
-		if err != nil {
-			return nil, nil, xerrors.Errorf("commit: %w", err)
-		}
-
-		cids, err := sb.SealPreCommit2(context.TODO(), sid, in2)
-		if err != nil {
-			return nil, nil, xerrors.Errorf("commit: %w", err)
-		}
-
-		if err := sb.FinalizeSector(context.TODO(), sid, nil); err != nil {
-			return nil, nil, xerrors.Errorf("trim cache: %w", err)
-		}
-
-		if err := cleanupUnsealed(sbfs, sid); err != nil {
-			return nil, nil, xerrors.Errorf("remove unsealed file: %w", err)
-		}
-
-		log.Warn("PreCommitOutput: ", sid, cids.Sealed, cids.Unsealed)
-		sealedSectors = append(sealedSectors, &genesis.PreSeal{
-			CommR:     cids.Sealed,
-			CommD:     cids.Unsealed,
-			SectorID:  sid.Number,
-			ProofType: spt,
-		})
+		sealedSectors = append(sealedSectors, preseal)
 	}
 
 	var minerAddr *wallet.Key
@@ -165,6 +146,69 @@ func PreSeal(maddr address.Address, spt abi.RegisteredSealProof, offset abi.Sect
 	return miner, &minerAddr.KeyInfo, nil
 }
 
+func presealSector(sb *ffiwrapper.Sealer, sbfs *basicfs.Provider, sid abi.SectorID, spt abi.RegisteredSealProof, ssize abi.SectorSize, preimage []byte) (*genesis.PreSeal, error) {
+	pi, err := sb.AddPiece(context.TODO(), sid, nil, abi.PaddedPieceSize(ssize).Unpadded(), rand.Reader)
+	if err != nil {
+		return nil, err
+	}
+
+	trand := blake2b.Sum256(preimage)
+	ticket := abi.SealRandomness(trand[:])
+
+	fmt.Printf("sector-id: %d, piece info: %v\n", sid, pi)
+
+	in2, err := sb.SealPreCommit1(context.TODO(), sid, ticket, []abi.PieceInfo{pi})
+	if err != nil {
+		return nil, xerrors.Errorf("commit: %w", err)
+	}
+
+	cids, err := sb.SealPreCommit2(context.TODO(), sid, in2)
+	if err != nil {
+		return nil, xerrors.Errorf("commit: %w", err)
+	}
+
+	if err := sb.FinalizeSector(context.TODO(), sid, nil); err != nil {
+		return nil, xerrors.Errorf("trim cache: %w", err)
+	}
+
+	if err := cleanupUnsealed(sbfs, sid); err != nil {
+		return nil, xerrors.Errorf("remove unsealed file: %w", err)
+	}
+
+	log.Warn("PreCommitOutput: ", sid, cids.Sealed, cids.Unsealed)
+
+	return &genesis.PreSeal{
+		CommR:     cids.Sealed,
+		CommD:     cids.Unsealed,
+		SectorID:  sid.Number,
+		ProofType: spt,
+	}, nil
+}
+
+func presealSectorFake(sbfs *basicfs.Provider, sid abi.SectorID, spt abi.RegisteredSealProof, ssize abi.SectorSize) (*genesis.PreSeal, error) {
+	paths, done, err := sbfs.AcquireSector(context.TODO(), sid, 0, stores.FTSealed | stores.FTCache, true)
+	if err != nil {
+		return nil, xerrors.Errorf("acquire unsealed sector: %w", err)
+	}
+	defer done()
+
+	if err := os.Mkdir(paths.Cache, 0755); err != nil {
+		return nil, xerrors.Errorf("mkdir cache: %w", err)
+	}
+
+	commr, err := ffi.FauxRep(spt, paths.Cache, paths.Sealed)
+	if err != nil {
+		return nil, xerrors.Errorf("fauxrep: %w", err)
+	}
+
+	return &genesis.PreSeal{
+		CommR:     commr,
+		CommD:     zerocomm.ZeroPieceCommitment(abi.PaddedPieceSize(ssize).Unpadded()),
+		SectorID:  sid.Number,
+		ProofType: spt,
+	}, nil
+}
+
 func cleanupUnsealed(sbfs *basicfs.Provider, sid abi.SectorID) error {
 	paths, done, err := sbfs.AcquireSector(context.TODO(), sid, stores.FTUnsealed, stores.FTNone, stores.PathSealing)
 	if err != nil {
diff --git a/extern/filecoin-ffi b/extern/filecoin-ffi
index 5342c7c97..6a143e06f 160000
--- a/extern/filecoin-ffi
+++ b/extern/filecoin-ffi
@@ -1 +1 @@
-Subproject commit 5342c7c97d1a1df4650629d14f2823d52889edd9
+Subproject commit 6a143e06f923f3a4f544c7a652e8b4df420a3d28
diff --git a/lotuspond/spawn.go b/lotuspond/spawn.go
index 8100d784a..ef0ebaeab 100644
--- a/lotuspond/spawn.go
+++ b/lotuspond/spawn.go
@@ -49,7 +49,7 @@ func (api *api) Spawn() (nodeInfo, error) {
 		}
 
 		sbroot := filepath.Join(dir, "preseal")
-		genm, ki, err := seed.PreSeal(genMiner, abi.RegisteredSealProof_StackedDrg2KiBV1, 0, 2, sbroot, []byte("8"), nil)
+		genm, ki, err := seed.PreSeal(genMiner, abi.RegisteredSealProof_StackedDrg2KiBV1, 0, 2, sbroot, []byte("8"), nil, false)
 		if err != nil {
 			return nodeInfo{}, xerrors.Errorf("preseal failed: %w", err)
 		}
diff --git a/node/node_test.go b/node/node_test.go
index b9837b1f0..6f33c6c57 100644
--- a/node/node_test.go
+++ b/node/node_test.go
@@ -189,7 +189,7 @@ func builder(t *testing.T, nFull int, storage []test.StorageMiner) ([]test.TestN
 		if err != nil {
 			t.Fatal(err)
 		}
-		genm, k, err := seed.PreSeal(maddr, abi.RegisteredSealProof_StackedDrg2KiBV1, 0, test.GenesisPreseals, tdir, []byte("make genesis mem random"), nil)
+		genm, k, err := seed.PreSeal(maddr, abi.RegisteredSealProof_StackedDrg2KiBV1, 0, test.GenesisPreseals, tdir, []byte("make genesis mem random"), nil, true)
 		if err != nil {
 			t.Fatal(err)
 		}