diff --git a/packages/marshal/src/encodePassable.js b/packages/marshal/src/encodePassable.js
index 40369cb1ff..c24dc48be9 100644
--- a/packages/marshal/src/encodePassable.js
+++ b/packages/marshal/src/encodePassable.js
@@ -530,8 +530,8 @@ export const makeEncodePassable = (encodeOptions = {}) => {
     }
   };
   const encodePassable = xxx
-    ? // A leading "#" indicates the v2 encoding (with escaping in strings rather than arrays).
-      passable => `#${innerEncode(passable)}`
+    ? // A leading "~" indicates the v2 encoding (with escaping in strings rather than arrays).
+      passable => `~${innerEncode(passable)}`
     : innerEncode;
   return harden(encodePassable);
 };
@@ -618,8 +618,8 @@ export const makeDecodePassable = (decodeOptions = {}) => {
     return innerDecode;
   };
   const decodePassable = encoded => {
-    // A leading "#" indicates the v2 encoding (with escaping in strings rather than arrays).
-    if (encoded.startsWith('#')) {
+    // A leading "~" indicates the v2 encoding (with escaping in strings rather than arrays).
+    if (encoded.startsWith('~')) {
       const innerDecode = makeInnerDecode(
         decodeStringWithEscapes,
         decodeArrayWithoutEscapes,
diff --git a/packages/marshal/test/test-encodePassable.js b/packages/marshal/test/test-encodePassable.js
index 031cda5842..ee464131e3 100644
--- a/packages/marshal/test/test-encodePassable.js
+++ b/packages/marshal/test/test-encodePassable.js
@@ -133,10 +133,10 @@ const goldenPairs = harden([
 test('golden round trips', t => {
   for (const [k, e] of goldenPairs) {
     t.is(encodePassable(k), e, 'does k encode as expected');
-    t.is(encodePassable2(k), `#${e}`, 'does k small-encode as expected');
+    t.is(encodePassable2(k), `~${e}`, 'does k small-encode as expected');
     t.is(decodePassable(e), k, 'does the key round trip through the encoding');
     t.is(
-      decodePassable(`#${e}`),
+      decodePassable(`~${e}`),
       k,
       'does the small-encoded key round trip through the encoding',
     );