diff --git a/packages/marshal/test/test-marshal-capdata.js b/packages/marshal/test/test-marshal-capdata.js
index e0251a97e8..f4854083d7 100644
--- a/packages/marshal/test/test-marshal-capdata.js
+++ b/packages/marshal/test/test-marshal-capdata.js
@@ -154,12 +154,13 @@ test('unserialize errors', t => {
 });
 
 test('unserialize extended errors', t => {
+  if (typeof AggregateError === 'undefined') {
+    t.pass('skip test on platforms prior to AggregateError');
+    return;
+  }
   const { unserialize } = makeTestMarshal();
   const uns = body => unserialize({ body, slots: [] });
 
-  // TODO cause, errors, and AggregateError will eventually be recognized.
-  // See https://github.com/endojs/endo/pull/2042
-
   const refErr = uns(
     '{"@qclass":"error","message":"msg","name":"ReferenceError","extraProp":"foo","cause":"bar","errors":["zip","zap"]}',
   );
@@ -189,6 +190,10 @@ test('unserialize extended errors', t => {
 });
 
 test('unserialize errors w recognized extensions', t => {
+  if (typeof AggregateError === 'undefined') {
+    t.pass('skip test on platforms prior to AggregateError');
+    return;
+  }
   const { unserialize } = makeTestMarshal();
   const uns = body => unserialize({ body, slots: [] });
 
diff --git a/packages/marshal/test/test-marshal-smallcaps.js b/packages/marshal/test/test-marshal-smallcaps.js
index 9b285dbe02..86e75bdeca 100644
--- a/packages/marshal/test/test-marshal-smallcaps.js
+++ b/packages/marshal/test/test-marshal-smallcaps.js
@@ -160,6 +160,10 @@ test('smallcaps unserialize errors', t => {
 });
 
 test('smallcaps unserialize extended errors', t => {
+  if (typeof AggregateError === 'undefined') {
+    t.pass('skip test on platforms prior to AggregateError');
+    return;
+  }
   const { unserialize } = makeTestMarshal();
   const uns = body => unserialize({ body, slots: [] });
 
@@ -192,6 +196,10 @@ test('smallcaps unserialize extended errors', t => {
 });
 
 test('smallcaps unserialize errors w recognized extensions', t => {
+  if (typeof AggregateError === 'undefined') {
+    t.pass('skip test on platforms prior to AggregateError');
+    return;
+  }
   const { unserialize } = makeTestMarshal();
   const uns = body => unserialize({ body, slots: [] });
 
diff --git a/packages/pass-style/src/error.js b/packages/pass-style/src/error.js
index dc9d4afae5..5e70ec8baf 100644
--- a/packages/pass-style/src/error.js
+++ b/packages/pass-style/src/error.js
@@ -24,10 +24,17 @@ const errorConstructors = new Map(
     ['URIError', URIError],
 
     // https://github.com/endojs/endo/issues/550
-    ['AggregateError', AggregateError],
+    // To accommodate platforms prior to AggregateError, we comment out the
+    // following line and instead conditionally add it to the map below.
+    // ['AggregateError', AggregateError],
   ]),
 );
 
+if (typeof AggregateError !== 'undefined') {
+  // Conditional, to accommodate platforms prior to AggregateError
+  errorConstructors.set('AggregateError', AggregateError);
+}
+
 /**
  * Because the error constructor returned by this function might be
  * `AggregateError`, which has different construction parameters
diff --git a/packages/pass-style/src/passStyleOf.js b/packages/pass-style/src/passStyleOf.js
index 1f2ddb05a8..32b43db37b 100644
--- a/packages/pass-style/src/passStyleOf.js
+++ b/packages/pass-style/src/passStyleOf.js
@@ -299,7 +299,7 @@ export const assertPassableError = err => {
  * Return a new passable error that propagates the diagnostic info of the
  * original, and is linked to the original as a note.
  *
- * @param {Error | AggregateError} err
+ * @param {Error} err
  * @returns {Error}
  */
 export const toPassableError = err => {
diff --git a/packages/pass-style/test/test-extended-errors.js b/packages/pass-style/test/test-extended-errors.js
index 0f653bf39a..1f24f4b5e5 100644
--- a/packages/pass-style/test/test-extended-errors.js
+++ b/packages/pass-style/test/test-extended-errors.js
@@ -18,6 +18,9 @@ test('style of extended errors', t => {
   const u3 = harden(URIError('u3', { cause: e1 }));
   t.is(passStyleOf(u3), 'error');
 
-  const a4 = harden(AggregateError([e2, u3], 'a4', { cause: e1 }));
-  t.is(passStyleOf(a4), 'error');
+  if (typeof AggregateError !== 'undefined') {
+    // Conditional, to accommodate platforms prior to AggregateError
+    const a4 = harden(AggregateError([e2, u3], 'a4', { cause: e1 }));
+    t.is(passStyleOf(a4), 'error');
+  }
 });
diff --git a/packages/ses/src/error/assert.js b/packages/ses/src/error/assert.js
index 6dae9e3ae4..bacf5124c9 100644
--- a/packages/ses/src/error/assert.js
+++ b/packages/ses/src/error/assert.js
@@ -274,7 +274,10 @@ const makeError = (
   const messageString = getMessageString(hiddenDetails);
   const opts = cause && { cause };
   let error;
-  if (errConstructor === AggregateError) {
+  if (
+    typeof AggregateError !== 'undefined' &&
+    errConstructor === AggregateError
+  ) {
     error = AggregateError(errors || [], messageString, opts);
   } else {
     error = /** @type {ErrorConstructor} */ (errConstructor)(
diff --git a/packages/ses/src/permits.js b/packages/ses/src/permits.js
index bf3d33f4d2..611671dd6e 100644
--- a/packages/ses/src/permits.js
+++ b/packages/ses/src/permits.js
@@ -1,4 +1,8 @@
 /* eslint-disable no-restricted-globals */
+/* eslint max-lines: 0 */
+
+import { arrayPush } from './commons.js';
+
 /**
  * @file Exports {@code whitelist}, a recursively defined
  * JSON record enumerating all intrinsics and their properties
@@ -8,8 +12,6 @@
  * @author Mark S. Miller
  */
 
-/* eslint max-lines: 0 */
-
 /**
  * constantProperties
  * non-configurable, non-writable data properties of all global objects.
@@ -187,7 +189,8 @@ export const uniqueGlobalPropertyNames = {
 
 // All the "subclasses" of Error. These are collectively represented in the
 // ECMAScript spec by the meta variable NativeError.
-export const NativeErrors = [
+/** @type {GenericErrorConstructor[]} */
+const NativeErrors = [
   EvalError,
   RangeError,
   ReferenceError,
@@ -195,9 +198,18 @@ export const NativeErrors = [
   TypeError,
   URIError,
   // https://github.com/endojs/endo/issues/550
-  AggregateError,
+  // Commented out to accommodate platforms prior to AggregateError.
+  // Instead, conditional push below.
+  // AggregateError,
 ];
 
+if (typeof AggregateError !== 'undefined') {
+  // Conditional, to accommodate platforms prior to AggregateError
+  arrayPush(NativeErrors, AggregateError);
+}
+
+export { NativeErrors };
+
 /**
  * <p>Each JSON record enumerates the disposition of the properties on
  *    some corresponding intrinsic object.
diff --git a/packages/ses/test/error/test-aggregate-error-console-demo.js b/packages/ses/test/error/test-aggregate-error-console-demo.js
index 8472d7ce91..ba2da6ae16 100644
--- a/packages/ses/test/error/test-aggregate-error-console-demo.js
+++ b/packages/ses/test/error/test-aggregate-error-console-demo.js
@@ -10,6 +10,10 @@ import '../../index.js';
 lockdown();
 
 test('aggregate error console demo', t => {
+  if (typeof AggregateError === 'undefined') {
+    t.pass('skip test on platforms prior to AggregateError');
+    return;
+  }
   const e3 = Error('e3');
   const e2 = Error('e2', { cause: e3 });
   const u4 = URIError('u4', { cause: e2 });
diff --git a/packages/ses/test/error/test-aggregate-error-console.js b/packages/ses/test/error/test-aggregate-error-console.js
index 417fcc85c8..ba192546be 100644
--- a/packages/ses/test/error/test-aggregate-error-console.js
+++ b/packages/ses/test/error/test-aggregate-error-console.js
@@ -5,6 +5,10 @@ import { throwsAndLogs } from './throws-and-logs.js';
 lockdown();
 
 test('aggregate error console', t => {
+  if (typeof AggregateError === 'undefined') {
+    t.pass('skip test on platforms prior to AggregateError');
+    return;
+  }
   const e3 = Error('e3');
   const e2 = Error('e2', { cause: e3 });
   const u4 = URIError('u4', { cause: e2 });
diff --git a/packages/ses/test/error/test-aggregate-error.js b/packages/ses/test/error/test-aggregate-error.js
index a95fbd114c..5c0b0b2466 100644
--- a/packages/ses/test/error/test-aggregate-error.js
+++ b/packages/ses/test/error/test-aggregate-error.js
@@ -6,6 +6,10 @@ const { getOwnPropertyDescriptor } = Object;
 lockdown();
 
 test('aggregate error', t => {
+  if (typeof AggregateError === 'undefined') {
+    t.pass('skip test on platforms prior to AggregateError');
+    return;
+  }
   const e1 = Error('e1');
   const e2 = Error('e2', { cause: e1 });
   const u3 = URIError('u3', { cause: e1 });
@@ -28,6 +32,10 @@ test('aggregate error', t => {
 });
 
 test('Promise.any aggregate error', async t => {
+  if (typeof AggregateError === 'undefined') {
+    t.pass('skip test on platforms prior to AggregateError');
+    return;
+  }
   const e1 = Error('e1');
   const e2 = Error('e2', { cause: e1 });
   const u3 = URIError('u3', { cause: e1 });
diff --git a/packages/ses/test/error/test-error-cause.js b/packages/ses/test/error/test-error-cause.js
index 0416285afd..5cd32091f5 100644
--- a/packages/ses/test/error/test-error-cause.js
+++ b/packages/ses/test/error/test-error-cause.js
@@ -27,6 +27,10 @@ test('error cause', t => {
     enumerable: false,
     configurable: true,
   });
+  if (typeof AggregateError === 'undefined') {
+    t.pass('skip rest of test on platforms prior to AggregateError');
+    return;
+  }
   const a4 = AggregateError([e2, u3], 'a4', { cause: e1 });
   t.is(a4.message, 'a4');
   t.is(a4.cause, e1);