diff --git a/packages/ERTP/src/displayInfo.js b/packages/ERTP/src/displayInfo.js
index 5cc16e11342..abd7a1afb75 100644
--- a/packages/ERTP/src/displayInfo.js
+++ b/packages/ERTP/src/displayInfo.js
@@ -1,3 +1,5 @@
+// @jessie-check
+
 import { Fail } from '@agoric/assert';
 import { mustMatch } from '@agoric/store';
 
diff --git a/packages/ERTP/src/index.js b/packages/ERTP/src/index.js
index 9c446eecb2d..90b18683f5e 100644
--- a/packages/ERTP/src/index.js
+++ b/packages/ERTP/src/index.js
@@ -1,3 +1,5 @@
+// @jessie-check
+
 export * from './amountMath.js';
 export * from './issuerKit.js';
 export * from './typeGuards.js';
diff --git a/packages/ERTP/src/legacy-payment-helpers.js b/packages/ERTP/src/legacy-payment-helpers.js
index 4b4e503f304..30873d6c46d 100644
--- a/packages/ERTP/src/legacy-payment-helpers.js
+++ b/packages/ERTP/src/legacy-payment-helpers.js
@@ -1,3 +1,5 @@
+// @jessie-check
+
 import { mustMatch } from '@agoric/store';
 import { E } from '@endo/far';
 import { AmountMath } from './amountMath.js';
diff --git a/packages/ERTP/src/mathHelpers/copyBagMathHelpers.js b/packages/ERTP/src/mathHelpers/copyBagMathHelpers.js
index 197208b18a0..576bd2bc6c0 100644
--- a/packages/ERTP/src/mathHelpers/copyBagMathHelpers.js
+++ b/packages/ERTP/src/mathHelpers/copyBagMathHelpers.js
@@ -1,3 +1,5 @@
+// @jessie-check
+
 import {
   keyEQ,
   makeCopyBag,
diff --git a/packages/ERTP/src/mathHelpers/copySetMathHelpers.js b/packages/ERTP/src/mathHelpers/copySetMathHelpers.js
index 5b8bc35149e..c18501f00e5 100644
--- a/packages/ERTP/src/mathHelpers/copySetMathHelpers.js
+++ b/packages/ERTP/src/mathHelpers/copySetMathHelpers.js
@@ -1,3 +1,5 @@
+// @jessie-check
+
 import {
   keyEQ,
   makeCopySet,
diff --git a/packages/ERTP/src/mathHelpers/natMathHelpers.js b/packages/ERTP/src/mathHelpers/natMathHelpers.js
index f721fd32ccf..3528047297f 100644
--- a/packages/ERTP/src/mathHelpers/natMathHelpers.js
+++ b/packages/ERTP/src/mathHelpers/natMathHelpers.js
@@ -1,3 +1,5 @@
+// @jessie-check
+
 import { Nat, isNat } from '@endo/nat';
 
 import '../types-ambient.js';
diff --git a/packages/ERTP/src/mathHelpers/setMathHelpers.js b/packages/ERTP/src/mathHelpers/setMathHelpers.js
index c05779ef66f..87f2e22f44d 100644
--- a/packages/ERTP/src/mathHelpers/setMathHelpers.js
+++ b/packages/ERTP/src/mathHelpers/setMathHelpers.js
@@ -1,3 +1,5 @@
+// @jessie-check
+
 import { passStyleOf } from '@endo/marshal';
 import {
   assertKey,
diff --git a/packages/ERTP/src/payment.js b/packages/ERTP/src/payment.js
index 34d19db81df..9c3a0e64428 100644
--- a/packages/ERTP/src/payment.js
+++ b/packages/ERTP/src/payment.js
@@ -1,3 +1,5 @@
+// @jessie-check
+
 import { initEmpty } from '@agoric/store';
 import { prepareExoClass } from '@agoric/vat-data';
 
diff --git a/packages/ERTP/src/paymentLedger.js b/packages/ERTP/src/paymentLedger.js
index 7af3fd7fd52..330300b5e0f 100644
--- a/packages/ERTP/src/paymentLedger.js
+++ b/packages/ERTP/src/paymentLedger.js
@@ -1,3 +1,5 @@
+// @jessie-check
+
 /* eslint-disable no-use-before-define */
 import { isPromise } from '@endo/promise-kit';
 import { mustMatch, M, keyEQ } from '@agoric/store';
diff --git a/packages/ERTP/src/transientNotifier.js b/packages/ERTP/src/transientNotifier.js
index 0e612cf78b6..190ec705ce0 100644
--- a/packages/ERTP/src/transientNotifier.js
+++ b/packages/ERTP/src/transientNotifier.js
@@ -1,3 +1,5 @@
+// @jessie-check
+
 import { makeScalarBigWeakMapStore } from '@agoric/vat-data';
 import { provideLazy } from '@agoric/store';
 import { makeNotifierKit } from '@agoric/notifier';
diff --git a/packages/ERTP/src/typeGuards.js b/packages/ERTP/src/typeGuards.js
index 6e564478c08..22752f7daa4 100644
--- a/packages/ERTP/src/typeGuards.js
+++ b/packages/ERTP/src/typeGuards.js
@@ -1,3 +1,5 @@
+// @jessie-check
+
 import { M, matches } from '@agoric/store';
 
 export const BrandShape = M.remotable('Brand');
diff --git a/packages/ERTP/src/types-ambient.js b/packages/ERTP/src/types-ambient.js
index 6e911148960..b9734f14a57 100644
--- a/packages/ERTP/src/types-ambient.js
+++ b/packages/ERTP/src/types-ambient.js
@@ -1,3 +1,5 @@
+// @jessie-check
+
 /// <reference types="ses"/>
 
 /**