diff --git a/build/forks.go b/build/forks.go
index 35990bfbf..976b54d6c 100644
--- a/build/forks.go
+++ b/build/forks.go
@@ -1,3 +1,4 @@
 package build
 
 const ForkCCM = 1750
+const ForkNoPowerEPSUpdates = 20000
diff --git a/chain/actors/actor_miner.go b/chain/actors/actor_miner.go
index 9b3c871a3..2fb5c668f 100644
--- a/chain/actors/actor_miner.go
+++ b/chain/actors/actor_miner.go
@@ -238,7 +238,7 @@ func (sma StorageMinerActor) PreCommitSector(act *types.Actor, vmctx types.VMCon
 	}
 
 	if vmctx.Message().From != mi.Worker {
-		return nil, aerrors.New(1, "not authorized to commit sector for miner")
+		return nil, aerrors.New(1, "not authorized to precommit sector for miner")
 	}
 
 	// make sure the miner isnt trying to submit a pre-existing sector
@@ -303,6 +303,10 @@ func (sma StorageMinerActor) ProveCommitSector(act *types.Actor, vmctx types.VMC
 		return nil, err
 	}
 
+	if vmctx.Message().From != mi.Worker {
+		return nil, aerrors.New(1, "not authorized to sector proof for miner")
+	}
+
 	us, ok := self.PreCommittedSectors[uintToStringKey(params.SectorID)]
 	if !ok {
 		return nil, aerrors.New(1, "no pre-commitment found for sector")
@@ -368,7 +372,7 @@ func (sma StorageMinerActor) ProveCommitSector(act *types.Actor, vmctx types.VMC
 		return nil, aerrors.HandleExternalError(lerr, "could not load proving set node")
 	}
 
-	if pss.Count == 0 {
+	if pss.Count == 0 && (!self.Active || vmctx.BlockHeight() < build.ForkNoPowerEPSUpdates) { // FORK
 		self.ProvingSet = self.Sectors
 		// TODO: probably want to wait until the miner is above a certain
 		//  threshold before starting this
@@ -814,6 +818,15 @@ func (sma StorageMinerActor) DeclareFaults(act *types.Actor, vmctx types.VMConte
 		return nil, aerr
 	}
 
+	mi, aerr := loadMinerInfo(vmctx, self)
+	if aerr != nil {
+		return nil, aerr
+	}
+
+	if vmctx.Message().From != mi.Worker {
+		return nil, aerrors.New(1, "not authorized to declare faults for miner")
+	}
+
 	nfaults, err := types.MergeBitFields(params.Faults, self.FaultSet)
 	if err != nil {
 		return nil, aerrors.Absorb(err, 1, "failed to merge bitfields")
@@ -824,7 +837,7 @@ func (sma StorageMinerActor) DeclareFaults(act *types.Actor, vmctx types.VMConte
 	self.LastFaultSubmission = vmctx.BlockHeight()
 
 	nstate, aerr := vmctx.Storage().Put(self)
-	if err != nil { // TODO: FORK: should be aerr
+	if aerr != nil {
 		return nil, aerr
 	}
 	if err := vmctx.Storage().Commit(oldstate, nstate); err != nil {
@@ -965,6 +978,8 @@ func onSuccessfulPoSt(self *StorageMinerActorState, vmctx types.VMContext) aerro
 		if err != nil {
 			return aerrors.Wrap(err, "updating storage failed")
 		}
+
+		self.ElectionPeriodStart = vmctx.BlockHeight()
 	}
 
 	ncid, err := RemoveFromSectorSet(vmctx.Context(), vmctx.Storage(), self.Sectors, faults)
@@ -974,7 +989,9 @@ func onSuccessfulPoSt(self *StorageMinerActorState, vmctx types.VMContext) aerro
 
 	self.Sectors = ncid
 	self.ProvingSet = ncid
-	self.ElectionPeriodStart = vmctx.BlockHeight()
+	if vmctx.BlockHeight() < build.ForkNoPowerEPSUpdates { // FORK
+		self.ElectionPeriodStart = vmctx.BlockHeight()
+	}
 	return nil
 }
 
diff --git a/chain/actors/actor_storagepower.go b/chain/actors/actor_storagepower.go
index 8a6648ca6..2f164dbcb 100644
--- a/chain/actors/actor_storagepower.go
+++ b/chain/actors/actor_storagepower.go
@@ -393,7 +393,7 @@ func addMinerToBucket(vmctx types.VMContext, buckets *amt.Root, nextBucket uint6
 		return aerrors.HandleExternalError(err, "getting proving bucket")
 	}
 
-	err = bhamt.Set(vmctx.Context(), string(vmctx.Message().From.Bytes()), cborNull)
+	err = bhamt.Set(vmctx.Context(), string(vmctx.Message().From.Bytes()), CborNull)
 	if err != nil {
 		return aerrors.HandleExternalError(err, "setting miner in proving bucket")
 	}
@@ -768,7 +768,7 @@ func MinerSetRemove(ctx context.Context, vmctx types.VMContext, rcid cid.Cid, ma
 
 type cbgNull struct{}
 
-var cborNull = &cbgNull{}
+var CborNull = &cbgNull{}
 
 func (cbgNull) MarshalCBOR(w io.Writer) error {
 	n, err := w.Write(cbg.CborNull)
diff --git a/chain/stmgr/fork_no_p_eps.go b/chain/stmgr/fork_no_p_eps.go
new file mode 100644
index 000000000..0d01a01ba
--- /dev/null
+++ b/chain/stmgr/fork_no_p_eps.go
@@ -0,0 +1,122 @@
+package stmgr
+
+import (
+	"context"
+
+	"github.com/filecoin-project/go-amt-ipld"
+	"github.com/ipfs/go-cid"
+	"github.com/ipfs/go-hamt-ipld"
+	cbor "github.com/ipfs/go-ipld-cbor"
+	"github.com/whyrusleeping/cbor-gen"
+	"golang.org/x/xerrors"
+
+	"github.com/filecoin-project/lotus/build"
+	"github.com/filecoin-project/lotus/chain/actors"
+	"github.com/filecoin-project/lotus/chain/address"
+	"github.com/filecoin-project/lotus/chain/state"
+	"github.com/filecoin-project/lotus/chain/types"
+)
+
+func (sm *StateManager) forkNoPowerEPS(ctx context.Context, pstate cid.Cid) (cid.Cid, error) {
+	cst := hamt.CSTFromBstore(sm.cs.Blockstore())
+	st, err := state.LoadStateTree(cst, pstate)
+	if err != nil {
+		return cid.Undef, xerrors.Errorf("loading parent state tree: %w", err)
+	}
+
+	if err := st.MutateActor(actors.StoragePowerAddress, func(spa *types.Actor) error {
+		var head actors.StoragePowerState
+		if err := cst.Get(ctx, spa.Head, &head); err != nil {
+			return xerrors.Errorf("reading StoragePower state: %w", err)
+		}
+
+		buckets, err := amt.LoadAMT(amt.WrapBlockstore(sm.cs.Blockstore()), head.ProvingBuckets)
+		if err != nil {
+			return xerrors.Errorf("opening proving buckets AMT: %w", err)
+		}
+
+		fixedBuckets := map[uint64]map[address.Address]struct{}{}
+
+		if err := buckets.ForEach(func(bucketId uint64, ent *typegen.Deferred) error {
+			var bcid cid.Cid
+			if err := cbor.DecodeInto(ent.Raw, &bcid); err != nil {
+				return xerrors.Errorf("decoding bucket cid: %w", err)
+			}
+
+			bucket, err := hamt.LoadNode(ctx, cst, bcid)
+			if err != nil {
+				return xerrors.Errorf("loading bucket hamt: %w", err)
+			}
+
+			return bucket.ForEach(ctx, func(abytes string, _ interface{}) error {
+				addr, err := address.NewFromBytes([]byte(abytes))
+				if err != nil {
+					return xerrors.Errorf("parsing address in proving bucket: %w", err)
+				}
+
+				// now find the correct bucket
+				miner, err := st.GetActor(addr)
+				if err != nil {
+					return xerrors.Errorf("getting miner %s: %w", addr, err)
+				}
+
+				var minerHead actors.StorageMinerActorState
+				if err := cst.Get(ctx, miner.Head, &minerHead); err != nil {
+					return xerrors.Errorf("reading miner %s state: %w", addr, err)
+				}
+
+				correctBucket := minerHead.ElectionPeriodStart % build.SlashablePowerDelay
+				if correctBucket != bucketId {
+					log.Warnf("miner %s was in wrong proving bucket %d, putting in %d (eps: %d)", addr, bucketId, correctBucket, minerHead.ElectionPeriodStart)
+				}
+
+				if _, ok := fixedBuckets[correctBucket]; !ok {
+					fixedBuckets[correctBucket] = map[address.Address]struct{}{}
+				}
+				fixedBuckets[correctBucket][addr] = struct{}{}
+
+				return nil
+			})
+		}); err != nil {
+			return err
+		}
+
+		// /////
+		// Write fixed buckets
+
+		fixed := amt.NewAMT(amt.WrapBlockstore(sm.cs.Blockstore()))
+
+		for bucketId, addrss := range fixedBuckets {
+			bucket := hamt.NewNode(cst)
+			for addr := range addrss {
+				if err := bucket.Set(ctx, string(addr.Bytes()), actors.CborNull); err != nil {
+					return xerrors.Errorf("setting address in bucket: %w", err)
+				}
+			}
+
+			if err := bucket.Flush(ctx); err != nil {
+				return xerrors.Errorf("flushing bucket amt: %w", err)
+			}
+
+			bcid, err := cst.Put(context.TODO(), bucket)
+			if err != nil {
+				return xerrors.Errorf("put bucket: %w", err)
+			}
+
+			if err := fixed.Set(bucketId, bcid); err != nil {
+				return xerrors.Errorf("set bucket: %w", err)
+			}
+		}
+
+		spa.Head, err = fixed.Flush()
+		if err != nil {
+			return xerrors.Errorf("flushing bucket amt: %w", err)
+		}
+
+		return nil
+	}); err != nil {
+		return cid.Undef, err
+	}
+
+	return st.Flush()
+}
diff --git a/chain/stmgr/forks.go b/chain/stmgr/forks.go
new file mode 100644
index 000000000..90fcf974b
--- /dev/null
+++ b/chain/stmgr/forks.go
@@ -0,0 +1,17 @@
+package stmgr
+
+import (
+	"context"
+	"github.com/ipfs/go-cid"
+
+	"github.com/filecoin-project/lotus/build"
+)
+
+func (sm *StateManager) handleStateForks(ctx context.Context, pstate cid.Cid, height uint64) (cid.Cid, error) {
+	switch height {
+	case build.ForkNoPowerEPSUpdates: // TODO: +1?
+		return sm.forkNoPowerEPS(ctx, pstate)
+	default:
+		return pstate, nil
+	}
+}
diff --git a/chain/stmgr/stmgr.go b/chain/stmgr/stmgr.go
index bd3e16032..782e7decf 100644
--- a/chain/stmgr/stmgr.go
+++ b/chain/stmgr/stmgr.go
@@ -119,7 +119,10 @@ func (sm *StateManager) computeTipSetState(ctx context.Context, blks []*types.Bl
 		}
 	}
 
-	pstate := blks[0].ParentStateRoot
+	pstate, err := sm.handleStateForks(ctx, blks[0].ParentStateRoot, blks[0].Height)
+	if err != nil {
+		return cid.Undef, cid.Undef, xerrors.Errorf("error handling state forks: %w", err)
+	}
 
 	cids := make([]cid.Cid, len(blks))
 	for i, v := range blks {