diff --git a/vms/proposervm/block.go b/vms/proposervm/block.go
index 9c2ac8a3c38a..893b8a9eec01 100644
--- a/vms/proposervm/block.go
+++ b/vms/proposervm/block.go
@@ -183,6 +183,7 @@ func (p *postForkCommonComponents) buildChild(
 	ctx context.Context,
 	parentID ids.ID,
 	parentTimestamp time.Time,
+	parentHeight uint64,
 	parentPChainHeight uint64,
 ) (Block, error) {
 	// Child's timestamp is the later of now and this block's timestamp
@@ -203,13 +204,24 @@ func (p *postForkCommonComponents) buildChild(
 		return nil, err
 	}
 
-	buildUnsignedBlock, err := p.shouldBuildBlock(
-		ctx,
-		parentID,
-		parentTimestamp,
-		parentPChainHeight,
-		newTimestamp,
-	)
+	buildUnsignedBlock := true
+	if p.vm.IsDurangoActivated(parentTimestamp) {
+		err = p.shouldPostDurangoBuildBlock(
+			ctx,
+			parentTimestamp,
+			parentHeight,
+			parentPChainHeight,
+			newTimestamp,
+		)
+	} else {
+		buildUnsignedBlock, err = p.shouldPreDurangoBuildBlock(
+			ctx,
+			parentID,
+			parentTimestamp,
+			parentPChainHeight,
+			newTimestamp,
+		)
+	}
 	if err != nil {
 		return nil, err
 	}
@@ -361,7 +373,25 @@ func (p *postForkCommonComponents) verifyPostDurangoBlockDelay(
 	return nil
 }
 
-func (p *postForkCommonComponents) shouldBuildBlock(
+func (p *postForkCommonComponents) shouldPostDurangoBuildBlock(
+	ctx context.Context,
+	parentTimestamp time.Time,
+	parentHeight uint64,
+	parentPChainHeight uint64,
+	newTimestamp time.Time,
+) error {
+	expectedProposerID, err := p.vm.Windower.ExpectedProposer(ctx, parentHeight+1, parentPChainHeight, newTimestamp, parentTimestamp)
+	if err != nil {
+		return err
+	}
+	if expectedProposerID != p.vm.ctx.NodeID {
+		return errProposerWindowNotStarted
+	}
+
+	return nil
+}
+
+func (p *postForkCommonComponents) shouldPreDurangoBuildBlock(
 	ctx context.Context,
 	parentID ids.ID,
 	parentTimestamp time.Time,
diff --git a/vms/proposervm/block_test.go b/vms/proposervm/block_test.go
index b3fd8d0d5dbc..478a92c334f5 100644
--- a/vms/proposervm/block_test.go
+++ b/vms/proposervm/block_test.go
@@ -40,10 +40,11 @@ func TestPostForkCommonComponents_buildChild(t *testing.T) {
 	pChainHeight := uint64(1337)
 	parentID := ids.GenerateTestID()
 	parentTimestamp := time.Now()
+	parentHeight := uint64(1234)
 	blkID := ids.GenerateTestID()
 	innerBlk := snowman.NewMockBlock(ctrl)
 	innerBlk.EXPECT().ID().Return(blkID).AnyTimes()
-	innerBlk.EXPECT().Height().Return(pChainHeight - 1).AnyTimes()
+	innerBlk.EXPECT().Height().Return(parentHeight + 1).AnyTimes()
 	builtBlk := snowman.NewMockBlock(ctrl)
 	builtBlk.EXPECT().Bytes().Return([]byte{1, 2, 3}).AnyTimes()
 	builtBlk.EXPECT().ID().Return(ids.GenerateTestID()).AnyTimes()
@@ -85,6 +86,7 @@ func TestPostForkCommonComponents_buildChild(t *testing.T) {
 		context.Background(),
 		parentID,
 		parentTimestamp,
+		parentHeight,
 		pChainHeight-1,
 	)
 	require.NoError(err)
diff --git a/vms/proposervm/post_fork_block.go b/vms/proposervm/post_fork_block.go
index 28d127d33f70..bea8ead5d851 100644
--- a/vms/proposervm/post_fork_block.go
+++ b/vms/proposervm/post_fork_block.go
@@ -149,6 +149,7 @@ func (b *postForkBlock) buildChild(ctx context.Context) (Block, error) {
 		ctx,
 		b.ID(),
 		b.Timestamp(),
+		b.Height(),
 		b.PChainHeight(),
 	)
 }
diff --git a/vms/proposervm/post_fork_option.go b/vms/proposervm/post_fork_option.go
index 047a01c477fd..fa3f86cbcca1 100644
--- a/vms/proposervm/post_fork_option.go
+++ b/vms/proposervm/post_fork_option.go
@@ -121,6 +121,7 @@ func (b *postForkOption) buildChild(ctx context.Context) (Block, error) {
 		ctx,
 		parentID,
 		b.Timestamp(),
+		b.Height(),
 		parentPChainHeight,
 	)
 }