diff --git a/CHANGELOG.md b/CHANGELOG.md
index 951bf7c351..117c3236f3 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,11 +1,11 @@
 # 0.91.0-beta.x
 
 - The `getRuntimeVersion` and `subscribeRuntimeVersion` RPCs are now only available on the `rpc.state.*` endpoints. This aligns with the Substrate implementation.
+- The `author_insertKey` RPC's last argument `publicKey` is now required, as to reflect Substrate implementation.
 - Support for extrinsics with versions that is not in the base Substrate implementation (V1-V3) can now be done by providing an implementation for `ExtrinsicUnknown`
 - **Breaking change** SignerPayload is registered and can be overrode now.
   - SignerPayload is renamed to SignerPayloadJSON
   - SignerPayloadJSON, SignerPayloadRawBase and SignerPayloadRaw are all moved to `@polkadot/types`
-  
 
 # 0.90.1
 
diff --git a/packages/rpc-core/src/jsonrpc.types.ts b/packages/rpc-core/src/jsonrpc.types.ts
index 7de10cd2d8..f8afc2539d 100644
--- a/packages/rpc-core/src/jsonrpc.types.ts
+++ b/packages/rpc-core/src/jsonrpc.types.ts
@@ -10,7 +10,7 @@ import { Codec, IExtrinsic } from '@polkadot/types/types';
 
 export interface RpcInterface {
   author: {
-    insertKey(keyType: Text | string, suri: Text | string, maybePublic?: Bytes | Uint8Array | string): Observable<Bytes>;
+    insertKey(keyType: Text | string, suri: Text | string, publicKey: Bytes | Uint8Array | string): Observable<Bytes>;
     pendingExtrinsics(): Observable<Vec<Extrinsic>>;
     removeExtrinsic(bytesOrHash: (ExtrinsicOrHash)[]): Observable<Vec<Hash>>;
     rotateKeys(): Observable<Bytes>;
diff --git a/packages/type-jsonrpc/src/author.ts b/packages/type-jsonrpc/src/author.ts
index 7de6535a80..f972870e98 100644
--- a/packages/type-jsonrpc/src/author.ts
+++ b/packages/type-jsonrpc/src/author.ts
@@ -20,7 +20,7 @@ const insertKey: RpcMethodOpt = {
   params: [
     createParam('keyType', 'Text'),
     createParam('suri', 'Text'),
-    createParam('maybePublic', 'Bytes', { isOptional: true })
+    createParam('publicKey', 'Bytes')
   ],
   type: 'Bytes'
 };