diff --git a/CHANGELOG.md b/CHANGELOG.md
index 5e5f2e7786..bae354f951 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -9,6 +9,7 @@ Changes:
 - Fix generate of well-known storage keys (e.g. `:code`)
 - Optimize metadata unknown type validation
 - Allow metadata creation for `Map` or `Record`
+- Added explicit double-byte ss58 `AccountId` encoding test
 - Update to latest Substrate metadata
 
 
diff --git a/packages/types/src/generic/AccountId.spec.ts b/packages/types/src/generic/AccountId.spec.ts
index 4003577a6f..8ecc214473 100644
--- a/packages/types/src/generic/AccountId.spec.ts
+++ b/packages/types/src/generic/AccountId.spec.ts
@@ -28,7 +28,9 @@ describe('AccountId', (): void => {
 
     it('allows decoding from null', (): void => {
       expect(
-        registry.createType('AccountId', null).eq('5C4hrfjw9DjXZTzV3MwzrrAr9P1MJhSrvWGWqi1eSuyUpnhM')
+        registry
+          .createType('AccountId', null)
+          .eq('5C4hrfjw9DjXZTzV3MwzrrAr9P1MJhSrvWGWqi1eSuyUpnhM')
       ).toBe(true);
     });
   });
@@ -36,9 +38,11 @@ describe('AccountId', (): void => {
   describe('decoding', (): void => {
     const testDecode = (type: string, input: Uint8Array | string | AccountId, expected: string): void =>
       it(`can decode from ${type}`, (): void => {
-        const a = registry.createType('AccountId', input);
-
-        expect(a.toString()).toBe(expected);
+        expect(
+          registry
+            .createType('AccountId', input)
+            .toString()
+        ).toBe(expected);
       });
 
     it('fails with non-32-byte lengths', (): void => {
@@ -75,9 +79,9 @@ describe('AccountId', (): void => {
   describe('encoding', (): void => {
     const testEncode = (to: 'toHex' | 'toJSON' | 'toString' | 'toU8a', expected: Uint8Array | string, input = '5C62W7ELLAAfix9LYrcx5smtcffbhvThkM5x7xfMeYXCtGwF'): void =>
       it(`can encode ${to}`, (): void => {
-        const a = registry.createType('AccountId', input);
-
-        expect(a[to]()).toEqual(expected);
+        expect(
+          registry.createType('AccountId', input)[to]()
+        ).toEqual(expected);
       });
 
     testEncode('toHex', '0x0102030405060708010203040506070801020304050607080102030405060708');
@@ -90,12 +94,34 @@ describe('AccountId', (): void => {
     ]));
 
     it('decodes to a non-empty value', (): void => {
-      expect(registry.createType('AccountId', 'FVU8T5yaAssHAUwo3PnKso7fqNthEqJZGCZgJZSR9cKjWAf').isEmpty).toBe(false);
+      expect(
+        registry
+          .createType('AccountId', 'FVU8T5yaAssHAUwo3PnKso7fqNthEqJZGCZgJZSR9cKjWAf')
+          .isEmpty
+      ).toBe(false);
+    });
+
+    it('encodes a 2-byte key correctly', (): void => {
+      const registry = new TypeRegistry();
+
+      registry.setChainProperties(
+        registry.createType('ChainProperties', {
+          ss58Format: 252
+        })
+      );
+
+      expect(
+        registry
+          .createType('AccountId', '0x5c64f1151f0ce4358c27238fb20c88e7c899825436f565410724c8c2c5add869')
+          .toString()
+      ).toEqual('xw5g1Eec8LT99pZLZMaTWwrwvNtfM6vrSuZeVbtEszCDUwByg');
     });
   });
 
   describe('storage decoding', (): void => {
     it('has the correct entries', (): void => {
+      const registry = new TypeRegistry();
+
       registry.setChainProperties(
         registry.createType('ChainProperties', {
           ss58Format: 2
@@ -103,9 +129,12 @@ describe('AccountId', (): void => {
       );
 
       const data = registry.createType('StorageData', jsonVec.params.result.changes[0][1]);
-      const list = registry.createType('Vec<AccountId>', data).map((accountId) => accountId.toString());
 
-      expect(list).toEqual([
+      expect(
+        registry
+          .createType('Vec<AccountId>', data)
+          .map((accountId) => accountId.toString())
+      ).toEqual([
         'FXmrFbdg2VdG1NttGTx1S6Czbv2SQ7PaD2PfryGBWWgt52i',
         'ELSnAoxwXaRP5i4RPjs6m1K3AGVCfXpt8GjTcrgtxvrAuZv',
         'EaoT1Mn6H3N9Ui3WdiLGTdKgjGChbrpLfnNV5zSLJLhZvgj',
diff --git a/packages/types/src/generic/AccountId.ts b/packages/types/src/generic/AccountId.ts
index d9fc8da4d3..601c7462d6 100644
--- a/packages/types/src/generic/AccountId.ts
+++ b/packages/types/src/generic/AccountId.ts
@@ -14,13 +14,13 @@ function decodeAccountId (value?: AnyU8a | AnyString): Uint8Array {
     return new Uint8Array();
   } else if (isU8a(value) || Array.isArray(value)) {
     return u8aToU8a(value);
-  } else if (isHex(value)) {
-    return hexToU8a(value.toString());
   } else if (isString(value)) {
-    return decodeAddress((value as string).toString());
+    return isHex(value)
+      ? hexToU8a(value.toString())
+      : decodeAddress((value as string).toString());
   }
 
-  throw new Error('Unknown type passed to AccountId constructor');
+  throw new Error(`Unknown type passed to AccountId constructor, found typeof ${typeof value}`);
 }
 
 /**