diff --git a/packages/non-trapping-shim/README.md b/packages/non-trapping-shim/README.md
index 1207ff7a0b..f4c99a04a4 100644
--- a/packages/non-trapping-shim/README.md
+++ b/packages/non-trapping-shim/README.md
@@ -1,4 +1,4 @@
-# Ponyfill and Shim for Non-trapping Integrity Trait
+# Shim for Non-trapping Integrity Trait
 
 Emulates support for the non-trapping integrity trait from the
 [Stabilize proposal](https://github.com/tc39/proposal-stabilize).
@@ -7,6 +7,8 @@ A *shim* attempts to be as full fidelity as practical an emulation of the propos
 
 A shim typically "exports" its functionality by adding properties to primordial objects. A ponyfill typically exports its functionality by explicit module exports, to be explicitly imported by code wishing to use it.
 
+This package is currently organized internally as a ponyfill, and a shim based on that ponyfill. But it no longer exports the ponyfill, as the [eval twin problems](https://github.com/endojs/endo/issues/1583) for using the ponyfill are fatal.
+
 See https://github.com/endojs/endo/blob/master/packages/ses/docs/preparing-for-stabilize.md for guidance on how to prepare for the changes that will be introduced by this proposal.
 
 TODO: More explanation.
diff --git a/packages/non-trapping-shim/index.js b/packages/non-trapping-shim/index.js
deleted file mode 100644
index e61784152d..0000000000
--- a/packages/non-trapping-shim/index.js
+++ /dev/null
@@ -1 +0,0 @@
-export * from './src/non-trapping-pony.js';
diff --git a/packages/non-trapping-shim/package.json b/packages/non-trapping-shim/package.json
index 0e22fb507b..315acd9aed 100644
--- a/packages/non-trapping-shim/package.json
+++ b/packages/non-trapping-shim/package.json
@@ -2,7 +2,7 @@
   "name": "@endo/non-trapping-shim",
   "version": "0.1.0",
   "private": true,
-  "description": "shim and ponyfill for non-trapping integrity trait",
+  "description": "shim of the non-trapping integrity trait",
   "keywords": [],
   "author": "Endo contributors",
   "license": "Apache-2.0",
@@ -19,7 +19,6 @@
   "main": "./index.js",
   "module": "./index.js",
   "exports": {
-    ".": "./index.js",
     "./shim.js": "./shim.js",
     "./package.json": "./package.json"
   },
diff --git a/packages/non-trapping-shim/src/non-trapping-pony.js b/packages/non-trapping-shim/src/non-trapping-pony.js
index 1428dea7d1..85590289a1 100644
--- a/packages/non-trapping-shim/src/non-trapping-pony.js
+++ b/packages/non-trapping-shim/src/non-trapping-pony.js
@@ -1,3 +1,8 @@
+// The exports of this ponyfill should only be used internally to this package
+// for separate unit testing, and for building the shim. The eval-twin
+// problems https://github.com/endojs/endo/issues/1583 with using a ponyfill
+// of this package are fatal, and so only the shim should be used externally.
+
 const OriginalObject = Object;
 const OriginalReflect = Reflect;
 const OriginalProxy = Proxy;
diff --git a/packages/non-trapping-shim/test/non-trapping-shim.test.js b/packages/non-trapping-shim/test/non-trapping-shim.test.js
index 9279928d29..6c4695aa8e 100644
--- a/packages/non-trapping-shim/test/non-trapping-shim.test.js
+++ b/packages/non-trapping-shim/test/non-trapping-shim.test.js
@@ -6,7 +6,7 @@ import '../shim.js';
 
 const { freeze, isFrozen } = Object;
 
-test('non-trapping-pony', async t => {
+test('non-trapping-shim', async t => {
   const specimen = { foo: 8 };
 
   const sillyHandler = freeze({