diff --git a/packages/types/package.json b/packages/types/package.json
index 8493e47738..887ef85f67 100644
--- a/packages/types/package.json
+++ b/packages/types/package.json
@@ -24,6 +24,7 @@
   "main": "index.js",
   "dependencies": {
     "@babel/runtime": "^7.16.3",
+    "@polkadot/types-known": "6.9.3-1",
     "@polkadot/util": "^7.9.2",
     "@polkadot/util-crypto": "^7.9.2",
     "rxjs": "^7.4.0"
diff --git a/packages/types/src/extrinsic/signedExtensions/index.ts b/packages/types/src/extrinsic/signedExtensions/index.ts
index 86ccfdf46f..539aa6277e 100644
--- a/packages/types/src/extrinsic/signedExtensions/index.ts
+++ b/packages/types/src/extrinsic/signedExtensions/index.ts
@@ -10,16 +10,17 @@ import { shell } from './shell';
 import { statemint } from './statemint';
 import { substrate } from './substrate';
 
-// A mapping of the known signed extensions to the extra fields that they contain. Unlike in the actual extensions,
-// we define the extra fields not as a Tuple, but rather as a struct so they can be named. These will be expanded
-// into the various fields when added to the payload (we only support V4 onwards with these, V3 and earlier are
-// deemed fixed and non-changeable)
+// A mapping of the known signed extensions to the extra fields that they
+// contain. Unlike in the actual extensions, we define the extra fields not
+// as a Tuple, but rather as a struct so they can be named. These will be
+// expanded into the various fields when added to the payload (we only
+// support V4 onwards with these, V3 and earlier are deemed fixed))
 export const allExtensions: ExtDef = objectSpread({}, substrate, polkadot, shell, statemint);
 
-// the v4 signed extensions prior to the point of exposing these to the metadata.
-// This may not match 100% with the current defaults and are used when not specified
-// in the metadata (which is for very old chains). The order is important here, as
-// applied by default
+// the v4 signed extensions prior to the point of exposing these to the
+// metadata. This may not match 100% with the current defaults and are used
+// when not specified in the metadata (which is for very old chains). The
+// order is important here, as applied by default
 export const fallbackExtensions = [
   'CheckVersion',
   'CheckGenesis',
@@ -39,7 +40,7 @@ export function findUnknownExtensions (extensions: string[], userExtensions: Ext
 export function expandExtensionTypes (extensions: string[], type: keyof ExtInfo, userExtensions: ExtDef = {}): ExtTypes {
   return extensions
     // Always allow user extensions first - these should provide overrides
-    .map((key) => userExtensions[key] || allExtensions[key])
+    .map((k) => userExtensions[k] || allExtensions[k])
     .filter((info): info is ExtInfo => !!info)
     .reduce((result, info): ExtTypes => objectSpread(result, info[type]), {});
 }
diff --git a/packages/types/src/extrinsic/v4/ExtrinsicPayload.ts b/packages/types/src/extrinsic/v4/ExtrinsicPayload.ts
index a4816f9dc2..d410cebca0 100644
--- a/packages/types/src/extrinsic/v4/ExtrinsicPayload.ts
+++ b/packages/types/src/extrinsic/v4/ExtrinsicPayload.ts
@@ -20,8 +20,8 @@ import { sign } from '../util';
 /**
  * @name GenericExtrinsicPayloadV4
  * @description
- * A signing payload for an [[Extrinsic]]. For the final encoding, it is variable length based
- * on the contents included
+ * A signing payload for an [[Extrinsic]]. For the final encoding, it is
+ * variable length based on the contents included
  */
 export class GenericExtrinsicPayloadV4 extends Struct {
   #signOptions: SignOptions;
@@ -33,8 +33,9 @@ export class GenericExtrinsicPayloadV4 extends Struct {
       registry.getSignedExtensionExtra()
     ), value);
 
-    // Do detection for the type of extrinsic, in the case of MultiSignature this is an
-    // enum, in the case of AnySignature, this is a Hash only (may be 64 or 65 bytes)
+    // Do detection for the type of extrinsic, in the case of MultiSignature
+    // this is an enum, in the case of AnySignature, this is a Hash only
+    // (which may be 64 or 65 bytes)
     this.#signOptions = {
       withType: registry.createType('ExtrinsicSignature') instanceof Enum
     };
@@ -108,10 +109,11 @@ export class GenericExtrinsicPayloadV4 extends Struct {
    * @description Sign the payload with the keypair
    */
   public sign (signerPair: IKeyringPair): Uint8Array {
-    // NOTE The `toU8a({ method: true })` argument is absolutely critical - we don't want the method (Bytes)
-    // to have the length prefix included. This means that the data-as-signed is un-decodable,
-    // but is also doesn't need the extra information, only the pure data (and is not decoded)
-    // ... The same applies to V1..V3, if we have a V5, carry move this comment to latest
+    // NOTE The `toU8a({ method: true })` argument is absolutely critical, we
+    // don't want the method (Bytes) to have the length prefix included. This
+    // means that the data-as-signed is un-decodable, but is also doesn't need
+    // the extra information, only the pure data (and is not decoded) ...
+    // The same applies to V1..V3, if we have a V5, carrythis comment
     return sign(this.registry, signerPair, this.toU8a({ method: true }), this.#signOptions);
   }
 }
diff --git a/yarn.lock b/yarn.lock
index 2194d25975..ac15d1853c 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -2092,6 +2092,7 @@ __metadata:
   dependencies:
     "@babel/runtime": ^7.16.3
     "@polkadot/keyring": ^7.9.2
+    "@polkadot/types-known": 6.9.3-1
     "@polkadot/types-support": 6.9.3-1
     "@polkadot/util": ^7.9.2
     "@polkadot/util-crypto": ^7.9.2