diff --git a/packages/marshal/test/marshal-test-data.js b/packages/marshal/test/marshal-test-data.js
index b4be1d07a5..bff0169760 100644
--- a/packages/marshal/test/marshal-test-data.js
+++ b/packages/marshal/test/marshal-test-data.js
@@ -1,4 +1,4 @@
-import { makeTagged } from '@endo/pass-style';
+import { makeTagged, toPassableError } from '@endo/pass-style';
 import {
   exampleAlice,
   exampleBob,
@@ -80,7 +80,7 @@ export const roundTripPairs = harden([
 
   // errors
   [
-    Error(),
+    toPassableError(Error()),
     {
       '@qclass': 'error',
       message: '',
@@ -88,7 +88,7 @@ export const roundTripPairs = harden([
     },
   ],
   [
-    ReferenceError('msg'),
+    toPassableError(ReferenceError('msg')),
     {
       '@qclass': 'error',
       message: 'msg',
@@ -96,7 +96,7 @@ export const roundTripPairs = harden([
     },
   ],
   [
-    ReferenceError('#msg'),
+    toPassableError(ReferenceError('#msg')),
     {
       '@qclass': 'error',
       message: '#msg',
@@ -265,7 +265,7 @@ export const unsortedSample = harden([
   exampleAlice,
   [],
   Symbol.for('foo'),
-  Error('not erroneous'),
+  toPassableError(Error('not erroneous')),
   Symbol.for('@@foo'),
   [5, { bar: 5 }],
   Symbol.for(''),
@@ -300,7 +300,7 @@ export const unsortedSample = harden([
   [Promise.resolve(null)],
 ]);
 
-const rejectedP = Promise.reject(Error('broken'));
+const rejectedP = Promise.reject(toPassableError(Error('broken')));
 rejectedP.catch(() => {}); // Suppress unhandled rejection warning/error
 
 /**
@@ -308,7 +308,7 @@ rejectedP.catch(() => {}); // Suppress unhandled rejection warning/error
  */
 export const sortedSample = harden([
   // All errors are tied.
-  Error('different'),
+  toPassableError(Error('different')),
 
   {},
 
diff --git a/packages/marshal/test/test-encodePassable.js b/packages/marshal/test/test-encodePassable.js
index 6583479efe..cf1b370cb0 100644
--- a/packages/marshal/test/test-encodePassable.js
+++ b/packages/marshal/test/test-encodePassable.js
@@ -3,7 +3,7 @@
 import test from '@endo/ses-ava/prepare-endo.js';
 
 import { fc } from '@fast-check/ava';
-import { Remotable } from '@endo/pass-style';
+import { Remotable, toPassableError } from '@endo/pass-style';
 import { arbPassable } from '@endo/pass-style/tools.js';
 import { Fail, q } from '@endo/errors';
 
@@ -199,7 +199,11 @@ test('capability encoding', t => {
     encodeError: (_err, encodeRecur) => forceSigil(encodeRecur(allAscii), '!'),
   };
 
-  const data = harden([Remotable(), new Promise(() => {}), Error('Foo')]);
+  const data = harden([
+    Remotable(),
+    new Promise(() => {}),
+    toPassableError(Error('Foo')),
+  ]);
   const decoders = Object.fromEntries(
     Object.keys(encoders).map((encoderName, i) => {
       const decoderName = encoderName.replace('encode', 'decode');
diff --git a/packages/marshal/test/test-marshal-smallcaps.js b/packages/marshal/test/test-marshal-smallcaps.js
index ce5f1a763a..ac6f51b921 100644
--- a/packages/marshal/test/test-marshal-smallcaps.js
+++ b/packages/marshal/test/test-marshal-smallcaps.js
@@ -11,6 +11,7 @@ const {
   create,
   prototype: objectPrototype,
   getPrototypeOf,
+  defineProperty,
 } = Object;
 
 const harden = /** @type {import('ses').Harden & { isFake?: boolean }} */ (
@@ -425,6 +426,9 @@ test('smallcaps encoding examples', t => {
   const nonPassableErr = Error('foo');
   // @ts-expect-error this type error is what we're testing
   nonPassableErr.extraProperty = 'something bad';
+  // Ensure that `stack` is a data property even on v8, so it does not
+  // first cause a different error than we're trying to test here.
+  defineProperty(nonPassableErr, 'stack', { value: nonPassableErr.stack });
   harden(nonPassableErr);
   t.throws(() => passStyleOf(nonPassableErr), {
     message:
diff --git a/packages/pass-style/test/test-errors.js b/packages/pass-style/test/test-errors.js
index 8ef7f607bc..2f08af0f58 100644
--- a/packages/pass-style/test/test-errors.js
+++ b/packages/pass-style/test/test-errors.js
@@ -8,23 +8,43 @@ import {
   toPassableError,
 } from '../src/passStyleOf.js';
 
-test('style of extended errors', t => {
-  const e1 = Error('e1');
-  t.throws(() => passStyleOf(e1), {
-    message: 'Cannot pass non-frozen objects like "[Error: e1]". Use harden()',
+test('style of extended toPassableError errors', t => {
+  const e1a = Error('e1a');
+  t.throws(() => passStyleOf(e1a), {
+    message: 'Cannot pass non-frozen objects like "[Error: e1a]". Use harden()',
   });
-  harden(e1);
+  const e1b = toPassableError(e1a);
+  t.is(passStyleOf(e1b), 'error');
+
+  const e2 = toPassableError(Error('e2', { cause: e1a }));
+  t.is(passStyleOf(e2), 'error');
+
+  const u3 = toPassableError(URIError('u3', { cause: e1a }));
+  t.is(passStyleOf(u3), 'error');
+
+  if (typeof AggregateError !== 'undefined') {
+    // Conditional, to accommodate platforms prior to AggregateError
+    const a4 = toPassableError(AggregateError([e2, u3], 'a4', { cause: e1a }));
+    t.is(passStyleOf(a4), 'error');
+  }
+});
+
+test('style of extended makeError errors', t => {
+  const e1 = makeError('e1c');
   t.is(passStyleOf(e1), 'error');
 
-  const e2 = harden(Error('e2', { cause: e1 }));
+  const e2 = makeError('e2', Error, { cause: e1 });
   t.is(passStyleOf(e2), 'error');
 
-  const u3 = harden(URIError('u3', { cause: e1 }));
+  const u3 = makeError('u3', URIError, { cause: e1 });
   t.is(passStyleOf(u3), 'error');
 
   if (typeof AggregateError !== 'undefined') {
     // Conditional, to accommodate platforms prior to AggregateError
-    const a4 = harden(AggregateError([e2, u3], 'a4', { cause: e1 }));
+    const a4 = toPassableError('a4', AggregateError, {
+      cause: e1,
+      errors: [e2, u3],
+    });
     t.is(passStyleOf(a4), 'error');
   }
 });
@@ -47,10 +67,4 @@ test('toPassableError rejects unfrozen errors', t => {
 
   t.true(Object.isFrozen(e2));
   t.true(isPassable(e2));
-
-  // May not be true on all platforms, depending on what "extraneous"
-  // properties the host added to the error before `makeError` returned it.
-  // If this fails, please let us know. See the doccomment on the
-  // `sanitizeError` function is the ses-shim's `assert.js`.
-  t.is(e, e2);
 });
diff --git a/packages/pass-style/test/test-passStyleOf.js b/packages/pass-style/test/test-passStyleOf.js
index baaa48dd2b..9ee167012e 100644
--- a/packages/pass-style/test/test-passStyleOf.js
+++ b/packages/pass-style/test/test-passStyleOf.js
@@ -1,9 +1,9 @@
 /* eslint-disable max-classes-per-file */
 import test from '@endo/ses-ava/prepare-endo.js';
 
-import { q } from '@endo/errors';
+import { q, makeError } from '@endo/errors';
 
-import { passStyleOf } from '../src/passStyleOf.js';
+import { passStyleOf, toPassableError } from '../src/passStyleOf.js';
 import { Far } from '../src/make-far.js';
 import { makeTagged } from '../src/makeTagged.js';
 import { PASS_STYLE } from '../src/passStyle-helpers.js';
@@ -28,7 +28,8 @@ test('passStyleOf basic success cases', t => {
   t.is(passStyleOf(harden({ then: 'non-function then ok' })), 'copyRecord');
   t.is(passStyleOf(harden({})), 'copyRecord', 'empty plain object');
   t.is(passStyleOf(makeTagged('unknown', undefined)), 'tagged');
-  t.is(passStyleOf(harden(Error('ok'))), 'error');
+  t.is(passStyleOf(makeError('ok')), 'error');
+  t.is(passStyleOf(toPassableError(Error('ok'))), 'error');
 });
 
 test('some passStyleOf rejections', t => {
@@ -415,7 +416,10 @@ test('Unexpected stack on errors', t => {
   }
 
   const carrierStack = {};
-  err.stack = carrierStack;
+  // Don't use assignment by itself, because on v8 that might leave
+  // stack as an accessor property, which would first cause a different
+  // that we're not testing here because it is platform dependent.
+  defineProperty(err, 'stack', { value: carrierStack });
   Object.freeze(err);
 
   t.throws(() => passStyleOf(err), {
diff --git a/packages/pass-style/tools/arb-passable.js b/packages/pass-style/tools/arb-passable.js
index 1d6651cdec..4c1117c9f7 100644
--- a/packages/pass-style/tools/arb-passable.js
+++ b/packages/pass-style/tools/arb-passable.js
@@ -1,4 +1,5 @@
 // @ts-check
+import { makeError } from '@endo/errors';
 import '../src/types.js';
 import { fc } from '@fast-check/ava';
 import { Far } from '../src/make-far.js';
@@ -31,7 +32,7 @@ export const arbLeaf = fc.oneof(
   fc.constantFrom(-0, NaN, Infinity, -Infinity),
   fc.record({}),
   fc.constantFrom(exampleAlice, exampleBob, exampleCarol),
-  arbString.map(s => Error(s)),
+  arbString.map(s => makeError(s)),
   // unresolved promise
   fc.constant(new Promise(() => {})),
 );