diff --git a/gen/builders/asserter.go b/gen/builders/asserter.go
index d02ea050..2d3f1d1b 100644
--- a/gen/builders/asserter.go
+++ b/gen/builders/asserter.go
@@ -4,12 +4,10 @@ import (
 	"fmt"
 	"os"
 
-	"github.com/filecoin-project/lotus/chain/state"
-
-	"github.com/filecoin-project/go-state-types/abi"
-
 	"github.com/filecoin-project/go-address"
-
+	"github.com/filecoin-project/go-state-types/abi"
+	"github.com/filecoin-project/go-state-types/exitcode"
+	"github.com/filecoin-project/lotus/chain/state"
 	"github.com/ipfs/go-cid"
 	"github.com/stretchr/testify/require"
 )
@@ -98,6 +96,11 @@ func (a *Asserter) HeadEq(addr address.Address, expected cid.Cid) {
 	a.Equal(expected, actor.Head, "expected actor %s head: %v, got: %v", addr, expected, actor.Head)
 }
 
+// ExitCodeEq verifies two exit codes are the same (and prints system codes nicely).
+func (a *Asserter) ExitCodeEq(actual exitcode.ExitCode, expected exitcode.ExitCode) {
+	a.Equal(expected, actual, "expected exit code: %s, got: %s", expected, actual)
+}
+
 // ActorExists verifies that the actor exists in the state tree.
 func (a *Asserter) ActorExists(addr address.Address) {
 	st := a.suppliers.stateTracker()
diff --git a/gen/suites/nested/main.go b/gen/suites/nested/main.go
index a29b512b..859f6d84 100644
--- a/gen/suites/nested/main.go
+++ b/gen/suites/nested/main.go
@@ -2,6 +2,7 @@ package main
 
 import (
 	. "github.com/filecoin-project/test-vectors/gen/builders"
+	"github.com/filecoin-project/test-vectors/schema"
 )
 
 func main() {
@@ -85,16 +86,22 @@ func main() {
 				ID:      "fail-missing-params",
 				Version: "v1",
 				Desc:    "",
+				Comment: "nested message exit code should be ErrSerialization see https://github.com/filecoin-project/test-vectors/issues/93#issuecomment-689593946",
 			},
 			MessageFunc: nestedSends_FailMissingParams,
+			Mode:        ModeLenientAssertions,
+			Hints:       []string{schema.HintIncorrect, schema.HintNegate},
 		},
 		&VectorDef{
 			Metadata: &Metadata{
 				ID:      "fail-mismatch-params",
 				Version: "v1",
 				Desc:    "",
+				Comment: "nested message exit code should be ErrSerialization see https://github.com/filecoin-project/test-vectors/issues/93#issuecomment-689593946",
 			},
 			MessageFunc: nestedSends_FailMismatchParams,
+			Mode:        ModeLenientAssertions,
+			Hints:       []string{schema.HintIncorrect, schema.HintNegate},
 		},
 		&VectorDef{
 			Metadata: &Metadata{
diff --git a/gen/suites/nested/nested.go b/gen/suites/nested/nested.go
index 48304a43..5738eae4 100644
--- a/gen/suites/nested/nested.go
+++ b/gen/suites/nested/nested.go
@@ -123,7 +123,11 @@ func nestedSends_FailNonexistentIDAddress(v *MessageVectorBuilder) {
 
 	newAddr := MustNewIDAddr(1234)
 	amtSent := abi.NewTokenAmount(1)
-	stage.sendOk(newAddr, amtSent, builtin.MethodSend, nil, nonce)
+	result := stage.sendOk(newAddr, amtSent, builtin.MethodSend, nil, nonce)
+
+	var ret multisig.ProposeReturn
+	MustDeserialize(result.Result.Return, &ret)
+	v.Assert.ExitCodeEq(ret.Code, exitcode.SysErrInvalidReceiver)
 
 	v.Assert.BalanceEq(stage.msAddr, multisigBalance) // No change.
 	v.Assert.ActorMissing(newAddr)
@@ -136,7 +140,11 @@ func nestedSends_FailNonexistentActorAddress(v *MessageVectorBuilder) {
 
 	newAddr := MustNewActorAddr("1234")
 	amtSent := abi.NewTokenAmount(1)
-	stage.sendOk(newAddr, amtSent, builtin.MethodSend, nil, nonce)
+	result := stage.sendOk(newAddr, amtSent, builtin.MethodSend, nil, nonce)
+
+	var ret multisig.ProposeReturn
+	MustDeserialize(result.Result.Return, &ret)
+	v.Assert.ExitCodeEq(ret.Code, exitcode.SysErrInvalidReceiver)
 
 	v.Assert.BalanceEq(stage.msAddr, multisigBalance) // No change.
 	v.Assert.ActorMissing(newAddr)
@@ -149,7 +157,11 @@ func nestedSends_FailInvalidMethodNumNewActor(v *MessageVectorBuilder) {
 
 	newAddr := v.Wallet.NewSECP256k1Account()
 	amtSent := abi.NewTokenAmount(1)
-	stage.sendOk(newAddr, amtSent, abi.MethodNum(99), nil, nonce)
+	result := stage.sendOk(newAddr, amtSent, abi.MethodNum(99), nil, nonce)
+
+	var ret multisig.ProposeReturn
+	MustDeserialize(result.Result.Return, &ret)
+	v.Assert.ExitCodeEq(ret.Code, exitcode.SysErrInvalidMethod)
 
 	v.Assert.BalanceEq(stage.msAddr, multisigBalance) // No change.
 	v.Assert.ActorMissing(newAddr)
@@ -164,6 +176,10 @@ func nestedSends_FailInvalidMethodNumForActor(v *MessageVectorBuilder) {
 	amtSent := abi.NewTokenAmount(1)
 	result := stage.sendOk(stage.creator, amtSent, abi.MethodNum(99), nil, nonce)
 
+	var ret multisig.ProposeReturn
+	MustDeserialize(result.Result.Return, &ret)
+	v.Assert.ExitCodeEq(ret.Code, exitcode.SysErrInvalidMethod)
+
 	v.Assert.BalanceEq(stage.msAddr, multisigBalance)                                           // No change.
 	v.Assert.BalanceEq(stage.creator, big.Sub(balanceBefore, CalculateSenderDeduction(result))) // Pay gas, don't receive funds.
 }
@@ -178,6 +194,10 @@ func nestedSends_FailMissingParams(v *MessageVectorBuilder) {
 	amtSent := abi.NewTokenAmount(1)
 	result := stage.sendOk(stage.msAddr, amtSent, builtin.MethodsMultisig.AddSigner, params, nonce)
 
+	var ret multisig.ProposeReturn
+	MustDeserialize(result.Result.Return, &ret)
+	v.Assert.ExitCodeEq(ret.Code, exitcode.ErrSerialization)
+
 	v.Assert.BalanceEq(stage.creator, big.Sub(balanceBefore, CalculateSenderDeduction(result)))
 	v.Assert.BalanceEq(stage.msAddr, multisigBalance) // No change.
 	v.Assert.Equal(1, len(stage.state().Signers))     // No new signers
@@ -199,6 +219,10 @@ func nestedSends_FailMismatchParams(v *MessageVectorBuilder) {
 	amtSent := abi.NewTokenAmount(1)
 	result := stage.sendOk(stage.msAddr, amtSent, builtin.MethodsMultisig.AddSigner, &params, nonce)
 
+	var ret multisig.ProposeReturn
+	MustDeserialize(result.Result.Return, &ret)
+	v.Assert.ExitCodeEq(ret.Code, exitcode.ErrSerialization)
+
 	v.Assert.BalanceEq(stage.creator, big.Sub(balanceBefore, CalculateSenderDeduction(result)))
 	v.Assert.BalanceEq(stage.msAddr, multisigBalance) // No change.
 	v.Assert.Equal(1, len(stage.state().Signers))     // No new signers
@@ -217,7 +241,11 @@ func nestedSends_FailInnerAbort(v *MessageVectorBuilder) {
 		GasReward: big.Zero(),
 	}
 	amtSent := abi.NewTokenAmount(1)
-	stage.sendOk(builtin.RewardActorAddr, amtSent, builtin.MethodsReward.AwardBlockReward, &params, nonce)
+	result := stage.sendOk(builtin.RewardActorAddr, amtSent, builtin.MethodsReward.AwardBlockReward, &params, nonce)
+
+	var ret multisig.ProposeReturn
+	MustDeserialize(result.Result.Return, &ret)
+	v.Assert.ExitCodeEq(ret.Code, exitcode.SysErrForbidden)
 
 	v.Assert.BalanceEq(stage.msAddr, multisigBalance) // No change.
 	v.Assert.HeadEq(builtin.RewardActorAddr, prevHead)
@@ -240,7 +268,11 @@ func nestedSends_FailAbortedExec(v *MessageVectorBuilder) {
 	}
 
 	amtSent := abi.NewTokenAmount(1)
-	stage.sendOk(builtin.InitActorAddr, amtSent, builtin.MethodsInit.Exec, &execParams, nonce)
+	result := stage.sendOk(builtin.InitActorAddr, amtSent, builtin.MethodsInit.Exec, &execParams, nonce)
+
+	var ret multisig.ProposeReturn
+	MustDeserialize(result.Result.Return, &ret)
+	v.Assert.ExitCodeEq(ret.Code, exitcode.ErrForbidden)
 
 	v.Assert.BalanceEq(stage.msAddr, multisigBalance) // No change.
 	v.Assert.HeadEq(builtin.InitActorAddr, prevHead)  // Init state unchanged.