diff --git a/cli/paych_test.go b/cli/paych_test.go
index f79300230..65d3d8d2e 100644
--- a/cli/paych_test.go
+++ b/cli/paych_test.go
@@ -5,6 +5,7 @@ import (
 	"context"
 	"flag"
 	"fmt"
+	"github.com/filecoin-project/specs-actors/actors/builtin/power"
 	"os"
 	"regexp"
 	"strconv"
@@ -42,6 +43,9 @@ func init() {
 		abi.RegisteredSealProof_StackedDrg2KiBV1: {},
 	}
 	verifreg.MinVerifiedDealSize = big.NewInt(256)
+
+	power.InitialQAPowerEstimatePosition = big.Zero()
+	power.InitialQAPowerEstimateVelocity = big.Zero()
 }
 
 // TestPaymentChannels does a basic test to exercise the payment channel CLI
diff --git a/storage/wdpost_run.go b/storage/wdpost_run.go
index 7b512d9d3..2e0ed1c84 100644
--- a/storage/wdpost_run.go
+++ b/storage/wdpost_run.go
@@ -421,10 +421,12 @@ func (s *WindowPoStScheduler) runPost(ctx context.Context, di miner.DeadlineInfo
 
 	elapsed := time.Since(tsStart)
 
-	commRand, err := s.api.ChainGetRandomnessFromTickets(ctx, ts.Key(), crypto.DomainSeparationTag_PoStChainCommit, di.Challenge, nil)
+	commEpoch := di.Open
+	commRand, err := s.api.ChainGetRandomnessFromTickets(ctx, ts.Key(), crypto.DomainSeparationTag_PoStChainCommit, commEpoch, nil)
 	if err != nil {
 		return nil, xerrors.Errorf("failed to get chain randomness for windowPost (ts=%d; deadline=%d): %w", ts.Height(), di, err)
 	}
+	params.ChainCommitEpoch = commEpoch
 	params.ChainCommitRand = commRand
 
 	log.Infow("submitting window PoSt", "elapsed", elapsed)