diff --git a/packages/cosmic-proto/src/address-hooks.js b/packages/cosmic-proto/src/address-hooks.js
index 073f0783c71f..c4c39645c7dd 100644
--- a/packages/cosmic-proto/src/address-hooks.js
+++ b/packages/cosmic-proto/src/address-hooks.js
@@ -44,7 +44,7 @@ if ((ADDRESS_HOOK_VERSION & 0x0f) !== ADDRESS_HOOK_VERSION) {
 const ADDRESS_HOOK_MAGIC = new Uint8Array([
   0x78,
   0xf1,
-  0x70 | ADDRESS_HOOK_VERSION,
+  0x70, // | ADDRESS_HOOK_VERSION
 ]);
 
 /**
@@ -145,6 +145,7 @@ export const joinHookedAddress = (
     magicLength + b + hd + BASE_ADDRESS_LENGTH_BYTES,
   );
   hookBuf.set(ADDRESS_HOOK_MAGIC, 0);
+  hookBuf[magicLength - 1] |= ADDRESS_HOOK_VERSION;
   hookBuf.set(bytes, magicLength);
   hookBuf.set(hookData, magicLength + b);
 
@@ -204,12 +205,23 @@ export const splitHookedAddressUnsafe = (
   const { prefix, bytes } = decodeBech32(specimen, charLimit);
 
   const magicLength = ADDRESS_HOOK_MAGIC.length;
+  let version = 0xff;
   for (let i = 0; i < magicLength; i += 1) {
-    if (bytes[i] !== ADDRESS_HOOK_MAGIC[i]) {
+    let maybeMagicByte = bytes[i];
+    if (i === magicLength - 1) {
+      // Final byte has a low version nibble and a high magic nibble.
+      version = maybeMagicByte & 0x0f;
+      maybeMagicByte &= 0xf0;
+    }
+    if (maybeMagicByte !== ADDRESS_HOOK_MAGIC[i]) {
       return { baseAddress: specimen, hookData: new Uint8Array() };
     }
   }
 
+  if (version !== ADDRESS_HOOK_VERSION) {
+    return `Unsupported address hook version ${version}`;
+  }
+
   let len = 0;
   for (let i = BASE_ADDRESS_LENGTH_BYTES - 1; i >= 0; i -= 1) {
     const byte = bytes.at(-i - 1);
diff --git a/packages/cosmic-proto/test/address-hooks.test.js b/packages/cosmic-proto/test/address-hooks.test.js
index 31ce2334f102..a216fc3159d5 100644
--- a/packages/cosmic-proto/test/address-hooks.test.js
+++ b/packages/cosmic-proto/test/address-hooks.test.js
@@ -42,6 +42,62 @@ test.before(async t => {
   t.context = await makeTestContext();
 });
 
+/**
+ * @type {import('ava').Macro<
+ *  [addressHook: string, baseAddress: string, hookDataStr: string, error?: any],
+ *   { addressHooks: import('../src/address-hooks.js') }
+ * >}
+ */
+const splitMacro = test.macro({
+  title(providedTitle = '', addressHook, _baseAddress, _hookDataStr, _error) {
+    return `${providedTitle} split ${addressHook}`;
+  },
+  exec(t, addressHook, baseAddress, hookDataStr, error) {
+    const { splitHookedAddress } = t.context.addressHooks;
+    if (error) {
+      t.throws(() => splitHookedAddress(addressHook), error);
+      return;
+    }
+    const { baseAddress: ba, hookData: hd } = splitHookedAddress(addressHook);
+    t.is(ba, baseAddress);
+    const hookData = new TextEncoder().encode(hookDataStr);
+    t.deepEqual(hd, hookData);
+  },
+});
+
+test('empty', splitMacro, '', '', '', { message: ' too short' });
+test('no hook', splitMacro, 'agoric1qqp0e5ys', 'agoric1qqp0e5ys', '', '');
+test(
+  'Fast USDC',
+  splitMacro,
+  'agoric10rchp4vc53apxn32q42c3zryml8xq3xshyzuhjk6405wtxy7tl3d7e0f8az423padaek6me38qekget2vdhx66mtvy6kg7nrw5uhsaekd4uhwufswqex6dtsv44hxv3cd4jkuqpqvduyhf',
+  'agoric16kv2g7snfc4q24vg3pjdlnnqgngtjpwtetd2h689nz09lcklvh5s8u37ek',
+  '?EUD=osmo183dejcnmkka5dzcu9xw6mywq0p2m5peks28men',
+);
+test(
+  'version 0',
+  splitMacro,
+  'agoric10rchqqqpqgpsgpgxquyqjzstpsxsurcszyfpxpqrqgqsq9qx0p9wp',
+  'agoric1qqqsyqcyq5rqwzqfpg9scrgwpugpzysn3tn9p0',
+  '\x04\x03\x02\x01',
+);
+test(
+  'version 1 reject',
+  splitMacro,
+  'agoric10rchzqqpqgpsgpgxquyqjzstpsxsurcszyfpxpqrqgqsq9q04n2fg',
+  '',
+  '',
+  { message: 'Unsupported address hook version 1' },
+);
+test(
+  'version 15 reject',
+  splitMacro,
+  'agoric10rch7qqpqgpsgpgxquyqjzstpsxsurcszyfpxpqrqgqsq9q25ez2d',
+  '',
+  '',
+  { message: 'Unsupported address hook version 15' },
+);
+
 /**
  * @type {import('ava').Macro<
  *   [string, ArrayLike<number> | undefined, ArrayLike<number>, string],