diff --git a/mock/mock.go b/mock/mock.go
index b21b82d34..3a3c8bb5f 100644
--- a/mock/mock.go
+++ b/mock/mock.go
@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"io"
 	"io/ioutil"
+	"math"
 	"math/rand"
 	"sync"
 
@@ -247,11 +248,24 @@ func AddOpFinish(ctx context.Context) (context.Context, func()) {
 }
 
 func (mgr *SectorMgr) GenerateWinningPoSt(ctx context.Context, minerID abi.ActorID, sectorInfo []abi.SectorInfo, randomness abi.PoStRandomness) ([]abi.PoStProof, error) {
-	return []abi.PoStProof{}, nil
+	return generateFakePoSt(sectorInfo), nil
 }
 
 func (mgr *SectorMgr) GenerateWindowPoSt(ctx context.Context, minerID abi.ActorID, sectorInfo []abi.SectorInfo, randomness abi.PoStRandomness) ([]abi.PoStProof, error) {
-	return []abi.PoStProof{}, nil
+	return generateFakePoSt(sectorInfo), nil
+}
+
+func generateFakePoSt(sectorInfo []abi.SectorInfo) []abi.PoStProof {
+	se, err := sectorInfo[0].RegisteredProof.WindowPoStPartitionSectors()
+	if err != nil {
+		panic(err)
+	}
+	return []abi.PoStProof{
+		{
+			RegisteredProof: sectorInfo[0].RegisteredProof,
+			ProofBytes:      make([]byte, 192*int(math.Ceil(float64(len(sectorInfo))/float64(se)))),
+		},
+	}
 }
 
 func (mgr *SectorMgr) ReadPieceFromSealedSector(ctx context.Context, sectorID abi.SectorID, offset ffiwrapper.UnpaddedByteIndex, size abi.UnpaddedPieceSize, ticket abi.SealRandomness, commD cid.Cid) (io.ReadCloser, error) {