diff --git a/packages/marshal/test/test-marshal-stringify.js b/packages/marshal/test/test-marshal-stringify.js
index 4b33c9b302..3a0d2cdd3f 100644
--- a/packages/marshal/test/test-marshal-stringify.js
+++ b/packages/marshal/test/test-marshal-stringify.js
@@ -39,9 +39,11 @@ test('marshal stringify errors', t => {
     t.throws(() => stringify({}), {
       message: /Cannot pass non-frozen objects like .*. Use harden()/,
     });
+    // @ts-expect-error intentional error
     t.throws(() => stringify(harden(new Uint8Array(1))), {
       message: 'Cannot pass mutable typed arrays like "[Uint8Array]".',
     });
+    // @ts-expect-error intentional error
     t.throws(() => stringify(harden(new Int16Array(1))), {
       message: 'Cannot pass mutable typed arrays like "[Int16Array]".',
     });
diff --git a/packages/patterns/src/keys/checkKey.js b/packages/patterns/src/keys/checkKey.js
index 7a50eb9a3b..4cdd2334c1 100644
--- a/packages/patterns/src/keys/checkKey.js
+++ b/packages/patterns/src/keys/checkKey.js
@@ -102,6 +102,7 @@ harden(assertScalarKey);
 
 // @ts-expect-error Key does not satisfy WeakKey
 /** @type {WeakSet<Key>} */
+// @ts-expect-error Key does not satisfy WeakKey
 const keyMemo = new WeakSet();
 
 /**
diff --git a/packages/patterns/src/keys/copyBag.js b/packages/patterns/src/keys/copyBag.js
index 23be6278f8..9c09e7eef4 100644
--- a/packages/patterns/src/keys/copyBag.js
+++ b/packages/patterns/src/keys/copyBag.js
@@ -100,6 +100,7 @@ export const checkBagEntries = (bagEntries, check) => {
       );
     }
   }
+  // @ts-expect-error FIXME Key types
   return checkNoDuplicateKeys(bagEntries, undefined, check);
 };
 harden(checkBagEntries);
diff --git a/packages/patterns/src/keys/keycollection-operators.js b/packages/patterns/src/keys/keycollection-operators.js
index 8e2b46f465..75440a6761 100644
--- a/packages/patterns/src/keys/keycollection-operators.js
+++ b/packages/patterns/src/keys/keycollection-operators.js
@@ -27,6 +27,7 @@ const { quote: q, Fail } = assert;
  * @returns {IterableIterator<[import('../types.js').Key, V]>}
  */
 const generateFullSortedEntries = (entries, rankCompare, fullCompare) => {
+  // @ts-expect-error FIXME Key types
   assertRankSorted(entries, rankCompare);
   const { length } = entries;
   let i = 0;
@@ -56,8 +57,10 @@ const generateFullSortedEntries = (entries, rankCompare, fullCompare) => {
 
       // Sort the ties by `fullCompare`, enforce key uniqueness, and delegate to
       // a sub-iterator.
+      // @ts-expect-error FIXME Key types
       const sortedTies = sortByRank(ties, fullCompare);
       for (let k = 1; k < sortedTies.length; k += 1) {
+        // @ts-expect-error FIXME Key types
         const [key0] = sortedTies[k - 1];
         const [key1] = sortedTies[k];
         Math.sign(fullCompare(key0, key1)) ||
diff --git a/packages/patterns/src/keys/merge-bag-operators.js b/packages/patterns/src/keys/merge-bag-operators.js
index 2ae5675f24..fdfb4901f5 100644
--- a/packages/patterns/src/keys/merge-bag-operators.js
+++ b/packages/patterns/src/keys/merge-bag-operators.js
@@ -72,6 +72,7 @@ const bagWindowResort = (bagEntries, rankCompare, fullCompare) => {
             // Providing the same `fullCompare` should cause a memo hit
             // within `assertNoDuplicates` enabling it to avoid a
             // redundant resorting.
+            // @ts-expect-error FIXME Key types
             assertNoDuplicateKeys(resorted, fullCompare);
             // This is the raw JS array iterator whose `.next()` method
             // does not harden the IteratorResult, in violation of our