diff --git a/itests/kit/blockminer.go b/itests/kit/blockminer.go
index 91ddc2e26e0..a232d82e026 100644
--- a/itests/kit/blockminer.go
+++ b/itests/kit/blockminer.go
@@ -3,6 +3,7 @@ package kit
 import (
 	"bytes"
 	"context"
+	"fmt"
 	"sync"
 	"sync/atomic"
 	"testing"
@@ -10,6 +11,7 @@ import (
 
 	"github.com/filecoin-project/go-bitfield"
 	"github.com/filecoin-project/go-state-types/abi"
+	"github.com/filecoin-project/go-state-types/dline"
 	"github.com/filecoin-project/lotus/api"
 	aminer "github.com/filecoin-project/lotus/chain/actors/builtin/miner"
 	"github.com/filecoin-project/lotus/chain/types"
@@ -63,11 +65,10 @@ func (p *partitionTracker) done(t *testing.T) bool {
 	return uint64(len(p.partitions)) == p.count(t)
 }
 
-func (p *partitionTracker) recordIfPost(t *testing.T, bm *BlockMiner, smsg *types.SignedMessage) (ret bool) {
+func (p *partitionTracker) recordIfPost(t *testing.T, bm *BlockMiner, msg *types.Message) (ret bool) {
 	defer func() {
 		ret = p.done(t)
 	}()
-	msg := smsg.Message
 	if !(msg.To == bm.miner.ActorAddr) {
 		return
 	}
@@ -82,11 +83,69 @@ func (p *partitionTracker) recordIfPost(t *testing.T, bm *BlockMiner, smsg *type
 	return
 }
 
+func (bm *BlockMiner) forcePoSt(ctx context.Context, ts *types.TipSet, dlinfo *dline.Info) {
+
+	tracker := newPartitionTracker(ctx, dlinfo.Index, bm)
+	if !tracker.done(bm.t) { // need to wait for post
+		bm.t.Logf("expect %d partitions proved but only see %d", len(tracker.partitions), tracker.count(bm.t))
+		poolEvts, err := bm.miner.FullNode.MpoolSub(ctx) //subscribe before checking pending so we don't miss any events
+		require.NoError(bm.t, err)
+
+		// First check pending messages we'll mine this epoch
+		msgs, err := bm.miner.FullNode.MpoolPending(ctx, types.EmptyTSK)
+		require.NoError(bm.t, err)
+		for _, msg := range msgs {
+			if tracker.recordIfPost(bm.t, bm, &msg.Message) {
+				fmt.Printf("found post in mempool pending\n")
+			}
+		}
+
+		// Account for included but not yet executed messages
+		for _, bc := range ts.Cids() {
+			msgs, err := bm.miner.FullNode.ChainGetBlockMessages(ctx, bc)
+			require.NoError(bm.t, err)
+			for _, msg := range msgs.BlsMessages {
+				if tracker.recordIfPost(bm.t, bm, msg) {
+					fmt.Printf("found post in message of prev tipset\n")
+				}
+
+			}
+			for _, msg := range msgs.SecpkMessages {
+				if tracker.recordIfPost(bm.t, bm, &msg.Message) {
+					fmt.Printf("found post in message of prev tipset\n")
+				}
+			}
+		}
+
+		// post not yet in mpool, wait for it
+		if !tracker.done(bm.t) {
+			bm.t.Logf("post missing from mpool, block mining suspended until it arrives")
+		POOL:
+			for {
+				bm.t.Logf("mpool event wait loop at block height %d, ts: %s", ts.Height(), ts.Key())
+				select {
+				case <-ctx.Done():
+					return
+				case evt := <-poolEvts:
+					bm.t.Logf("pool event: %d", evt.Type)
+					if evt.Type == api.MpoolAdd {
+						bm.t.Logf("incoming message %v", evt.Message)
+						if tracker.recordIfPost(bm.t, bm, &evt.Message.Message) {
+							fmt.Printf("found post in mempool evt\n")
+							break POOL
+						}
+					}
+				}
+			}
+			bm.t.Logf("done waiting on mpool")
+		}
+	}
+}
+
 // Like MineBlocks but refuses to mine until the window post scheduler has wdpost messages in the mempool
 // and everything shuts down if a post fails.  It also enforces that every block mined succeeds
 func (bm *BlockMiner) MineBlocksMustPost(ctx context.Context, blocktime time.Duration) {
-
-	time.Sleep(3 * time.Second)
+	time.Sleep(time.Second)
 
 	// wrap context in a cancellable context.
 	ctx, bm.cancel = context.WithCancel(ctx)
@@ -94,8 +153,6 @@ func (bm *BlockMiner) MineBlocksMustPost(ctx context.Context, blocktime time.Dur
 	go func() {
 		defer bm.wg.Done()
 
-		activeDeadlines := make(map[int]struct{})
-		_ = activeDeadlines
 		ts, err := bm.miner.FullNode.ChainHead(ctx)
 		require.NoError(bm.t, err)
 		wait := make(chan bool)
@@ -103,7 +160,7 @@ func (bm *BlockMiner) MineBlocksMustPost(ctx context.Context, blocktime time.Dur
 		require.NoError(bm.t, err)
 		// read current out
 		curr := <-chg
-		require.Equal(bm.t, ts.Height(), curr[0].Val.Height())
+		require.Equal(bm.t, ts.Height(), curr[0].Val.Height(), "failed sanity check: are multiple miners mining with must post?")
 		for {
 			select {
 			case <-time.After(blocktime):
@@ -111,52 +168,15 @@ func (bm *BlockMiner) MineBlocksMustPost(ctx context.Context, blocktime time.Dur
 				return
 			}
 			nulls := atomic.SwapInt64(&bm.nextNulls, 0)
-			require.Equal(bm.t, int64(0), nulls, "Injecting > 0 null blocks while `MustPost` mining is currently unsupported")
 
 			// Wake up and figure out if we are at the end of an active deadline
 			ts, err := bm.miner.FullNode.ChainHead(ctx)
 			require.NoError(bm.t, err)
-			tsk := ts.Key()
 
-			dlinfo, err := bm.miner.FullNode.StateMinerProvingDeadline(ctx, bm.miner.ActorAddr, tsk)
+			dlinfo, err := bm.miner.FullNode.StateMinerProvingDeadline(ctx, bm.miner.ActorAddr, ts.Key())
 			require.NoError(bm.t, err)
-			if ts.Height()+1 == dlinfo.Last() { // Last epoch in dline, we need to check that miner has posted
-
-				tracker := newPartitionTracker(ctx, dlinfo.Index, bm)
-				if !tracker.done(bm.t) { // need to wait for post
-					bm.t.Logf("expect %d partitions proved but only see %d", len(tracker.partitions), tracker.count(bm.t))
-					poolEvts, err := bm.miner.FullNode.MpoolSub(ctx)
-					require.NoError(bm.t, err)
-
-					// First check pending messages we'll mine this epoch
-					msgs, err := bm.miner.FullNode.MpoolPending(ctx, types.EmptyTSK)
-					require.NoError(bm.t, err)
-					for _, msg := range msgs {
-						tracker.recordIfPost(bm.t, bm, msg)
-					}
-
-					// post not yet in mpool, wait for it
-					if !tracker.done(bm.t) {
-						bm.t.Logf("post missing from mpool, block mining suspended until it arrives")
-					POOL:
-						for {
-							bm.t.Logf("mpool event wait loop at block height %d, ts: %s", ts.Height(), ts.Key())
-							select {
-							case <-ctx.Done():
-								return
-							case evt := <-poolEvts:
-								bm.t.Logf("pool event: %d", evt.Type)
-								if evt.Type == api.MpoolAdd {
-									bm.t.Logf("incoming message %v", evt.Message)
-									if tracker.recordIfPost(bm.t, bm, evt.Message) {
-										break POOL
-									}
-								}
-							}
-						}
-						bm.t.Logf("done waiting on mpool")
-					}
-				}
+			if ts.Height()+1+abi.ChainEpoch(nulls) >= dlinfo.Last() { // Next block brings us past the last epoch in dline, we need to wait for miner to post
+				bm.forcePoSt(ctx, ts, dlinfo)
 			}
 
 			var target abi.ChainEpoch
@@ -173,6 +193,12 @@ func (bm *BlockMiner) MineBlocksMustPost(ctx context.Context, blocktime time.Dur
 					Done:        reportSuccessFn,
 				})
 				success = <-wait
+				if !success {
+					// if we are mining a new null block and it brings us past deadline boundary we need to wait for miner to post
+					if ts.Height()+1+abi.ChainEpoch(nulls+i) >= dlinfo.Last() {
+						bm.forcePoSt(ctx, ts, dlinfo)
+					}
+				}
 			}
 
 			// Wait until it shows up on the given full nodes ChainHead
diff --git a/itests/paych_api_test.go b/itests/paych_api_test.go
index a07c499f9cf..7e135a9bea7 100644
--- a/itests/paych_api_test.go
+++ b/itests/paych_api_test.go
@@ -51,7 +51,7 @@ func TestPaymentChannelsAPI(t *testing.T) {
 		Miner(&miner, &paymentCreator, kit.WithAllSubsystems()).
 		Start().
 		InterconnectAll()
-	bms := ens.BeginMining(blockTime)
+	bms := ens.BeginMiningMustPost(blockTime)
 	bm := bms[0]
 
 	// send some funds to register the receiver