diff --git a/chain/actors/builtin/power/diff.go b/chain/actors/builtin/power/diff.go
new file mode 100644
index 000000000..3daa70569
--- /dev/null
+++ b/chain/actors/builtin/power/diff.go
@@ -0,0 +1,117 @@
+package power
+
+import (
+	"github.com/filecoin-project/go-address"
+	"github.com/filecoin-project/go-state-types/abi"
+	cbg "github.com/whyrusleeping/cbor-gen"
+
+	"github.com/filecoin-project/lotus/chain/actors/adt"
+)
+
+type ClaimChanges struct {
+	Added    []ClaimInfo
+	Modified []ClaimModification
+	Removed  []ClaimInfo
+}
+
+type ClaimModification struct {
+	Miner address.Address
+	From  Claim
+	To    Claim
+}
+
+type ClaimInfo struct {
+	Miner address.Address
+	Claim Claim
+}
+
+func DiffClaims(pre, cur State) (*ClaimChanges, error) {
+	results := new(ClaimChanges)
+
+	prec, err := pre.claims()
+	if err != nil {
+		return nil, err
+	}
+
+	curc, err := cur.claims()
+	if err != nil {
+		return nil, err
+	}
+
+	if err := adt.DiffAdtMap(prec, curc, &claimDiffer{results, pre, cur}); err != nil {
+		return nil, err
+	}
+
+	return results, nil
+}
+
+type claimDiffer struct {
+	Results    *ClaimChanges
+	pre, after State
+}
+
+func (c *claimDiffer) AsKey(key string) (abi.Keyer, error) {
+	addr, err := address.NewFromBytes([]byte(key))
+	if err != nil {
+		return nil, err
+	}
+	return abi.AddrKey(addr), nil
+}
+
+func (c *claimDiffer) Add(key string, val *cbg.Deferred) error {
+	ci, err := c.after.decodeClaim(val)
+	if err != nil {
+		return err
+	}
+	addr, err := address.NewFromBytes([]byte(key))
+	if err != nil {
+		return err
+	}
+	c.Results.Added = append(c.Results.Added, ClaimInfo{
+		Miner: addr,
+		Claim: ci,
+	})
+	return nil
+}
+
+func (c *claimDiffer) Modify(key string, from, to *cbg.Deferred) error {
+	ciFrom, err := c.pre.decodeClaim(from)
+	if err != nil {
+		return err
+	}
+
+	ciTo, err := c.after.decodeClaim(to)
+	if err != nil {
+		return err
+	}
+
+	addr, err := address.NewFromBytes([]byte(key))
+	if err != nil {
+		return err
+	}
+
+	if ciFrom != ciTo {
+		c.Results.Modified = append(c.Results.Modified, ClaimModification{
+			Miner: addr,
+			From:  ciFrom,
+			To:    ciTo,
+		})
+	}
+	return nil
+}
+
+func (c *claimDiffer) Remove(key string, val *cbg.Deferred) error {
+	ci, err := c.after.decodeClaim(val)
+	if err != nil {
+		return err
+	}
+	addr, err := address.NewFromBytes([]byte(key))
+	if err != nil {
+		return err
+	}
+	c.Results.Removed = append(c.Results.Removed, ClaimInfo{
+		Miner: addr,
+		Claim: ci,
+	})
+	return nil
+}
diff --git a/chain/actors/builtin/power/power.go b/chain/actors/builtin/power/power.go
index f941ce93e..e0cf0d700 100644
--- a/chain/actors/builtin/power/power.go
+++ b/chain/actors/builtin/power/power.go
@@ -4,6 +4,7 @@ import (
 	"github.com/filecoin-project/go-address"
 	"github.com/filecoin-project/go-state-types/big"
 	"github.com/ipfs/go-cid"
+	cbg "github.com/whyrusleeping/cbor-gen"
 	"golang.org/x/xerrors"
 
 	"github.com/filecoin-project/go-state-types/abi"
@@ -56,6 +57,11 @@ type State interface {
 	MinerNominalPowerMeetsConsensusMinimum(address.Address) (bool, error)
 	ListAllMiners() ([]address.Address, error)
 	ForEachClaim(func(miner address.Address, claim Claim) error) error
+	ClaimsChanged(State) (bool, error)
+
+	// Diff helpers. Used by Diff* functions internally.
+	claims() (adt.Map, error)
+	decodeClaim(*cbg.Deferred) (Claim, error)
 }
 
 type Claim struct {
diff --git a/chain/actors/builtin/power/v0.go b/chain/actors/builtin/power/v0.go
index 3f9a65777..7636b612b 100644
--- a/chain/actors/builtin/power/v0.go
+++ b/chain/actors/builtin/power/v0.go
@@ -1,9 +1,12 @@
 package power
 
 import (
+	"bytes"
+
 	"github.com/filecoin-project/go-address"
 	"github.com/filecoin-project/go-state-types/abi"
 	"github.com/ipfs/go-cid"
+	cbg "github.com/whyrusleeping/cbor-gen"
 
 	"github.com/filecoin-project/lotus/chain/actors/adt"
 	"github.com/filecoin-project/lotus/chain/actors/builtin"
@@ -115,3 +118,28 @@ func (s *state0) ForEachClaim(cb func(miner address.Address, claim Claim) error)
 		})
 	})
 }
+
+func (s *state0) ClaimsChanged(other State) (bool, error) {
+	other0, ok := other.(*state0)
+	if !ok {
+		// treat an upgrade as a change, always
+		return true, nil
+	}
+	return !s.State.Claims.Equals(other0.State.Claims), nil
+}
+
+func (s *state0) claims() (adt.Map, error) {
+	return adt0.AsMap(s.store, s.Claims)
+}
+
+func (s *state0) decodeClaim(val *cbg.Deferred) (Claim, error) {
+	var ci power0.Claim
+	if err := ci.UnmarshalCBOR(bytes.NewReader(val.Raw)); err != nil {
+		return Claim{}, err
+	}
+	return fromV0Claim(ci), nil
+}
+
+func fromV0Claim(v0 power0.Claim) Claim {
+	return (Claim)(v0)
+}
diff --git a/chain/actors/builtin/power/v2.go b/chain/actors/builtin/power/v2.go
index 0c15f0669..012dc2a4f 100644
--- a/chain/actors/builtin/power/v2.go
+++ b/chain/actors/builtin/power/v2.go
@@ -1,9 +1,12 @@
 package power
 
 import (
+	"bytes"
+
 	"github.com/filecoin-project/go-address"
 	"github.com/filecoin-project/go-state-types/abi"
 	"github.com/ipfs/go-cid"
+	cbg "github.com/whyrusleeping/cbor-gen"
 
 	"github.com/filecoin-project/lotus/chain/actors/adt"
 	"github.com/filecoin-project/lotus/chain/actors/builtin"
@@ -115,3 +118,31 @@ func (s *state2) ForEachClaim(cb func(miner address.Address, claim Claim) error)
 		})
 	})
 }
+
+func (s *state2) ClaimsChanged(other State) (bool, error) {
+	other2, ok := other.(*state2)
+	if !ok {
+		// treat an upgrade as a change, always
+		return true, nil
+	}
+	return !s.State.Claims.Equals(other2.State.Claims), nil
+}
+
+func (s *state2) claims() (adt.Map, error) {
+	return adt2.AsMap(s.store, s.Claims)
+}
+
+func (s *state2) decodeClaim(val *cbg.Deferred) (Claim, error) {
+	var ci power2.Claim
+	if err := ci.UnmarshalCBOR(bytes.NewReader(val.Raw)); err != nil {
+		return Claim{}, err
+	}
+	return fromV2Claim(ci), nil
+}
+
+func fromV2Claim(v2 power2.Claim) Claim {
+	return Claim{
+		RawBytePower:    v2.RawBytePower,
+		QualityAdjPower: v2.QualityAdjPower,
+	}
+}