diff --git a/packages/types/src/interfaces/session/definitions.ts b/packages/types/src/interfaces/session/definitions.ts
index 31d868ca31..a109f04ebe 100644
--- a/packages/types/src/interfaces/session/definitions.ts
+++ b/packages/types/src/interfaces/session/definitions.ts
@@ -11,8 +11,10 @@ export default {
     //   impl_opaque_keys! {
     //     pub struct SessionKeys {
     // Here we revert to tuples to keep the interfaces "opaque", as per the use
-    SessionKeysSubstrate: '(AccountId, AccountId, AccountId)', // Grandpa, Babe, ImOnline
-    SessionKeysPolkadot: '(AccountId, AccountId, AccountId)',
+    // For substrate: Grandpa, Babe, ImOnline
+    SessionKeysSubstrate: '(AccountId, AccountId, AccountId)',
+    // For polkadot: Grandpa, Babe, ImOnline, Parachains
+    SessionKeysPolkadot: '(AccountId, AccountId, AccountId, AccountId)',
     Keys: 'SessionKeysSubstrate'
   }
 };
diff --git a/packages/types/src/interfaces/session/types.ts b/packages/types/src/interfaces/session/types.ts
index 98b101f842..8883f137e7 100644
--- a/packages/types/src/interfaces/session/types.ts
+++ b/packages/types/src/interfaces/session/types.ts
@@ -11,8 +11,8 @@ export type Keys = SessionKeysSubstrate;
 /** u32 */
 export type SessionIndex = u32;
 
-/** [AccountId, AccountId, AccountId] & Codec */
-export type SessionKeysPolkadot = [AccountId, AccountId, AccountId] & Codec;
+/** [AccountId, AccountId, AccountId, AccountId] & Codec */
+export type SessionKeysPolkadot = [AccountId, AccountId, AccountId, AccountId] & Codec;
 
 /** [AccountId, AccountId, AccountId] & Codec */
 export type SessionKeysSubstrate = [AccountId, AccountId, AccountId] & Codec;