diff --git a/cmd/tvx/extract.go b/cmd/tvx/extract.go
index fef24585803..afdeb9540e3 100644
--- a/cmd/tvx/extract.go
+++ b/cmd/tvx/extract.go
@@ -198,8 +198,8 @@ func doExtract(ctx context.Context, fapi api.FullNode, opts extractOpts) error {
 			Preroot:    root,
 			Epoch:      execTs.Height(),
 			Message:    m,
-			CircSupply: &circSupplyDetail.FilCirculating,
-			BaseFee:    &basefee,
+			CircSupply: circSupplyDetail.FilCirculating,
+			BaseFee:    basefee,
 		})
 		if err != nil {
 			return fmt.Errorf("failed to execute precursor message: %w", err)
@@ -229,8 +229,8 @@ func doExtract(ctx context.Context, fapi api.FullNode, opts extractOpts) error {
 			Preroot:    preroot,
 			Epoch:      execTs.Height(),
 			Message:    msg,
-			CircSupply: &circSupplyDetail.FilCirculating,
-			BaseFee:    &basefee,
+			CircSupply: circSupplyDetail.FilCirculating,
+			BaseFee:    basefee,
 		})
 		if err != nil {
 			return fmt.Errorf("failed to execute message: %w", err)
@@ -260,8 +260,8 @@ func doExtract(ctx context.Context, fapi api.FullNode, opts extractOpts) error {
 			Preroot:    preroot,
 			Epoch:      execTs.Height(),
 			Message:    msg,
-			CircSupply: &circSupplyDetail.FilCirculating,
-			BaseFee:    &basefee,
+			CircSupply: circSupplyDetail.FilCirculating,
+			BaseFee:    basefee,
 		})
 		if err != nil {
 			return fmt.Errorf("failed to execute message: %w", err)
diff --git a/conformance/driver.go b/conformance/driver.go
index 9ced12d745a..d51798a525c 100644
--- a/conformance/driver.go
+++ b/conformance/driver.go
@@ -2,6 +2,7 @@ package conformance
 
 import (
 	"context"
+	gobig "math/big"
 	"os"
 
 	"github.com/filecoin-project/lotus/chain/state"
@@ -14,6 +15,7 @@ import (
 	"github.com/filecoin-project/lotus/lib/blockstore"
 
 	"github.com/filecoin-project/go-state-types/abi"
+	"github.com/filecoin-project/go-state-types/big"
 	"github.com/filecoin-project/go-state-types/crypto"
 
 	"github.com/filecoin-project/test-vectors/schema"
@@ -80,7 +82,7 @@ type ExecuteTipsetResult struct {
 func (d *Driver) ExecuteTipset(bs blockstore.Blockstore, ds ds.Batching, preroot cid.Cid, parentEpoch abi.ChainEpoch, tipset *schema.Tipset) (*ExecuteTipsetResult, error) {
 	var (
 		syscalls = mkFakedSigSyscalls(vm.Syscalls(ffiwrapper.ProofVerifier))
-		vmRand   = new(testRand)
+		vmRand   = NewFixedRand()
 
 		cs = store.NewChainStore(bs, ds, syscalls)
 		sm = stmgr.NewStateManager(cs)
@@ -143,8 +145,12 @@ type ExecuteMessageParams struct {
 	Preroot    cid.Cid
 	Epoch      abi.ChainEpoch
 	Message    *types.Message
-	CircSupply *abi.TokenAmount
-	BaseFee    *abi.TokenAmount
+	CircSupply abi.TokenAmount
+	BaseFee    abi.TokenAmount
+
+	// Rand is an optional vm.Rand implementation to use. If nil, the driver
+	// will use a vm.Rand that returns a fixed value for all calls.
+	Rand vm.Rand
 }
 
 // ExecuteMessage executes a conformance test vector message in a temporary VM.
@@ -155,14 +161,8 @@ func (d *Driver) ExecuteMessage(bs blockstore.Blockstore, params ExecuteMessageP
 		_ = os.Setenv("LOTUS_DISABLE_VM_BUF", "iknowitsabadidea")
 	}
 
-	basefee := DefaultBaseFee
-	if params.BaseFee != nil {
-		basefee = *params.BaseFee
-	}
-
-	circSupply := DefaultCirculatingSupply
-	if params.CircSupply != nil {
-		circSupply = *params.CircSupply
+	if params.Rand == nil {
+		params.Rand = NewFixedRand()
 	}
 
 	// dummy state manager; only to reference the GetNetworkVersion method,
@@ -172,13 +172,13 @@ func (d *Driver) ExecuteMessage(bs blockstore.Blockstore, params ExecuteMessageP
 	vmOpts := &vm.VMOpts{
 		StateBase: params.Preroot,
 		Epoch:     params.Epoch,
-		Rand:      &testRand{}, // TODO always succeeds; need more flexibility.
 		Bstore:    bs,
 		Syscalls:  mkFakedSigSyscalls(vm.Syscalls(ffiwrapper.ProofVerifier)), // TODO always succeeds; need more flexibility.
 		CircSupplyCalc: func(_ context.Context, _ abi.ChainEpoch, _ *state.StateTree) (abi.TokenAmount, error) {
-			return circSupply, nil
+			return params.CircSupply, nil
 		},
-		BaseFee:     basefee,
+		Rand:        params.Rand,
+		BaseFee:     params.BaseFee,
 		NtwkVersion: sm.GetNtwkVersion,
 	}
 
@@ -231,3 +231,22 @@ func toChainMsg(msg *types.Message) (ret types.ChainMsg) {
 	}
 	return ret
 }
+
+// BaseFeeOrDefault converts a basefee as passed in a test vector (go *big.Int
+// type) to an abi.TokenAmount, or if nil it returns the DefaultBaseFee.
+func BaseFeeOrDefault(basefee *gobig.Int) abi.TokenAmount {
+	if basefee == nil {
+		return DefaultBaseFee
+	}
+	return big.NewFromGo(basefee)
+}
+
+// CircSupplyOrDefault converts a circulating supply as passed in a test vector
+// (go *big.Int type) to an abi.TokenAmount, or if nil it returns the
+// DefaultCirculatingSupply.
+func CircSupplyOrDefault(circSupply *gobig.Int) abi.TokenAmount {
+	if circSupply == nil {
+		return DefaultBaseFee
+	}
+	return big.NewFromGo(circSupply)
+}
diff --git a/conformance/rand_fixed.go b/conformance/rand_fixed.go
new file mode 100644
index 00000000000..d356b53d049
--- /dev/null
+++ b/conformance/rand_fixed.go
@@ -0,0 +1,28 @@
+package conformance
+
+import (
+	"context"
+
+	"github.com/filecoin-project/go-state-types/abi"
+	"github.com/filecoin-project/go-state-types/crypto"
+
+	"github.com/filecoin-project/lotus/chain/vm"
+)
+
+type fixedRand struct{}
+
+var _ vm.Rand = (*fixedRand)(nil)
+
+// NewFixedRand creates a test vm.Rand that always returns fixed bytes value
+// of utf-8 string 'i_am_random_____i_am_random_____'.
+func NewFixedRand() vm.Rand {
+	return &fixedRand{}
+}
+
+func (r *fixedRand) GetChainRandomness(_ context.Context, _ crypto.DomainSeparationTag, _ abi.ChainEpoch, _ []byte) ([]byte, error) {
+	return []byte("i_am_random_____i_am_random_____"), nil // 32 bytes.
+}
+
+func (r *fixedRand) GetBeaconRandomness(_ context.Context, _ crypto.DomainSeparationTag, _ abi.ChainEpoch, _ []byte) ([]byte, error) {
+	return []byte("i_am_random_____i_am_random_____"), nil // 32 bytes.
+}
diff --git a/conformance/runner.go b/conformance/runner.go
index 2db53b3e4c3..a240c90678a 100644
--- a/conformance/runner.go
+++ b/conformance/runner.go
@@ -13,9 +13,7 @@ import (
 
 	"github.com/fatih/color"
 	"github.com/filecoin-project/go-state-types/abi"
-	"github.com/filecoin-project/go-state-types/big"
 	"github.com/filecoin-project/go-state-types/exitcode"
-	"github.com/filecoin-project/test-vectors/schema"
 	"github.com/ipfs/go-blockservice"
 	"github.com/ipfs/go-cid"
 	ds "github.com/ipfs/go-datastore"
@@ -24,6 +22,8 @@ import (
 	"github.com/ipfs/go-merkledag"
 	"github.com/ipld/go-car"
 
+	"github.com/filecoin-project/test-vectors/schema"
+
 	"github.com/filecoin-project/lotus/chain/types"
 	"github.com/filecoin-project/lotus/chain/vm"
 	"github.com/filecoin-project/lotus/lib/blockstore"
@@ -46,18 +46,6 @@ func ExecuteMessageVector(r Reporter, vector *schema.TestVector) {
 	// Create a new Driver.
 	driver := NewDriver(ctx, vector.Selector, DriverOpts{DisableVMFlush: true})
 
-	var circSupply *abi.TokenAmount
-	if cs := vector.Pre.CircSupply; cs != nil {
-		ta := big.NewFromGo(cs)
-		circSupply = &ta
-	}
-
-	var basefee *abi.TokenAmount
-	if bf := vector.Pre.BaseFee; bf != nil {
-		ta := big.NewFromGo(bf)
-		basefee = &ta
-	}
-
 	// Apply every message.
 	for i, m := range vector.ApplyMessages {
 		msg, err := types.DecodeMessage(m.Bytes)
@@ -76,8 +64,8 @@ func ExecuteMessageVector(r Reporter, vector *schema.TestVector) {
 			Preroot:    root,
 			Epoch:      abi.ChainEpoch(epoch),
 			Message:    msg,
-			CircSupply: circSupply,
-			BaseFee:    basefee,
+			BaseFee:    BaseFeeOrDefault(vector.Pre.BaseFee),
+			CircSupply: CircSupplyOrDefault(vector.Pre.CircSupply),
 		})
 		if err != nil {
 			r.Fatalf("fatal failure when executing message: %s", err)
diff --git a/conformance/stubs.go b/conformance/stubs.go
index a7100892f9c..9307fdd65a2 100644
--- a/conformance/stubs.go
+++ b/conformance/stubs.go
@@ -6,28 +6,16 @@ import (
 	"github.com/filecoin-project/specs-actors/actors/runtime/proof"
 
 	"github.com/filecoin-project/go-address"
+
 	"github.com/filecoin-project/lotus/chain/state"
 	"github.com/filecoin-project/lotus/chain/vm"
 
-	"github.com/filecoin-project/go-state-types/abi"
 	"github.com/filecoin-project/go-state-types/crypto"
 	"github.com/filecoin-project/specs-actors/actors/runtime"
 
 	cbor "github.com/ipfs/go-ipld-cbor"
 )
 
-type testRand struct{}
-
-var _ vm.Rand = (*testRand)(nil)
-
-func (r *testRand) GetChainRandomness(ctx context.Context, pers crypto.DomainSeparationTag, round abi.ChainEpoch, entropy []byte) ([]byte, error) {
-	return []byte("i_am_random_____i_am_random_____"), nil // 32 bytes.
-}
-
-func (r *testRand) GetBeaconRandomness(ctx context.Context, pers crypto.DomainSeparationTag, round abi.ChainEpoch, entropy []byte) ([]byte, error) {
-	return []byte("i_am_random_____i_am_random_____"), nil // 32 bytes.
-}
-
 type testSyscalls struct {
 	runtime.Syscalls
 }