diff --git a/cbor_gen.go b/cbor_gen.go
index eb6143ff7..42a54c103 100644
--- a/cbor_gen.go
+++ b/cbor_gen.go
@@ -132,7 +132,7 @@ func (t *DealInfo) MarshalCBOR(w io.Writer) error {
 		_, err := w.Write(cbg.CborNull)
 		return err
 	}
-	if _, err := w.Write([]byte{162}); err != nil {
+	if _, err := w.Write([]byte{163}); err != nil {
 		return err
 	}
 
@@ -167,6 +167,22 @@ func (t *DealInfo) MarshalCBOR(w io.Writer) error {
 	if err := t.DealSchedule.MarshalCBOR(w); err != nil {
 		return err
 	}
+
+	// t.KeepUnsealed (bool) (bool)
+	if len("KeepUnsealed") > cbg.MaxLength {
+		return xerrors.Errorf("Value in field \"KeepUnsealed\" was too long")
+	}
+
+	if _, err := w.Write(cbg.CborEncodeMajorType(cbg.MajTextString, uint64(len("KeepUnsealed")))); err != nil {
+		return err
+	}
+	if _, err := w.Write([]byte("KeepUnsealed")); err != nil {
+		return err
+	}
+
+	if err := cbg.WriteBool(w, t.KeepUnsealed); err != nil {
+		return err
+	}
 	return nil
 }
 
@@ -225,6 +241,24 @@ func (t *DealInfo) UnmarshalCBOR(r io.Reader) error {
 				}
 
 			}
+			// t.KeepUnsealed (bool) (bool)
+		case "KeepUnsealed":
+
+			maj, extra, err = cbg.CborReadHeader(br)
+			if err != nil {
+				return err
+			}
+			if maj != cbg.MajOther {
+				return fmt.Errorf("booleans must be major type 7")
+			}
+			switch extra {
+			case 20:
+				t.KeepUnsealed = false
+			case 21:
+				t.KeepUnsealed = true
+			default:
+				return fmt.Errorf("booleans are either major type 7, value 20 or 21 (got %d)", extra)
+			}
 
 		default:
 			return fmt.Errorf("unknown struct field %d: '%s'", i, name)
diff --git a/fsm.go b/fsm.go
index e0c53cfce..9f6580854 100644
--- a/fsm.go
+++ b/fsm.go
@@ -251,8 +251,7 @@ func (m *Sealing) plan(events []statemachine.Event, state *SectorInfo) (func(sta
 
 	// Post-seal
 	case Proving:
-		// TODO: track sector health / expiration
-		log.Infof("Proving sector %d", state.SectorNumber)
+		return m.handleProvingSector, nil
 	case Removing:
 		return m.handleRemoving, nil
 
diff --git a/states_sealing.go b/states_sealing.go
index 9659bce7b..113105162 100644
--- a/states_sealing.go
+++ b/states_sealing.go
@@ -356,9 +356,23 @@ func (m *Sealing) handleCommitWait(ctx statemachine.Context, sector SectorInfo)
 func (m *Sealing) handleFinalizeSector(ctx statemachine.Context, sector SectorInfo) error {
 	// TODO: Maybe wait for some finality
 
-	if err := m.sealer.FinalizeSector(sector.sealingCtx(ctx.Context()), m.minerSector(sector.SectorNumber), nil); err != nil {
+	if err := m.sealer.FinalizeSector(sector.sealingCtx(ctx.Context()), m.minerSector(sector.SectorNumber), sector.keepUnsealedRanges(false)); err != nil {
 		return ctx.Send(SectorFinalizeFailed{xerrors.Errorf("finalize sector: %w", err)})
 	}
 
 	return ctx.Send(SectorFinalized{})
 }
+
+func (m *Sealing) handleProvingSector(ctx statemachine.Context, sector SectorInfo) error {
+	// TODO: track sector health / expiration
+	log.Infof("Proving sector %d", sector.SectorNumber)
+
+	if err := m.sealer.ReleaseUnsealed(ctx.Context(), m.minerSector(sector.SectorNumber), sector.keepUnsealedRanges(true)); err != nil {
+		log.Error(err)
+	}
+
+	// TODO: Watch termination
+	// TODO: Auto-extend if set
+
+	return nil
+}
diff --git a/types.go b/types.go
index 41e1e0954..255c93a55 100644
--- a/types.go
+++ b/types.go
@@ -30,6 +30,7 @@ type Piece struct {
 type DealInfo struct {
 	DealID       abi.DealID
 	DealSchedule DealSchedule
+	KeepUnsealed bool
 }
 
 // DealSchedule communicates the time interval of a storage deal. The deal must
@@ -141,6 +142,32 @@ func (t *SectorInfo) sealingCtx(ctx context.Context) context.Context {
 	return ctx
 }
 
+// Returns list of offset/length tuples of sector data ranges which clients
+// requested to keep unsealed
+func (t *SectorInfo) keepUnsealedRanges(invert bool) []storage.Range {
+	var out []storage.Range
+
+	var at abi.UnpaddedPieceSize
+	for _, piece := range t.Pieces {
+		psize := piece.Piece.Size.Unpadded()
+		at += psize
+
+		if piece.DealInfo == nil {
+			continue
+		}
+		if piece.DealInfo.KeepUnsealed == invert {
+			continue
+		}
+
+		out = append(out, storage.Range{
+			Offset: at - psize,
+			Size:   psize,
+		})
+	}
+
+	return out
+}
+
 type SectorIDCounter interface {
 	Next() (abi.SectorNumber, error)
 }