diff --git a/packages/insomnia/src/network/basic-auth/get-header.ts b/packages/insomnia/src/network/basic-auth/get-header.ts
index 4439aa96f..670bedde6 100644
--- a/packages/insomnia/src/network/basic-auth/get-header.ts
+++ b/packages/insomnia/src/network/basic-auth/get-header.ts
@@ -3,11 +3,10 @@ import type { RequestHeader } from '../../models/request';
 export function getBasicAuthHeader(
   username?: string | null,
   password?: string | null,
-  encoding = 'utf8',
+  encoding: BufferEncoding = 'utf8',
 ) {
   const name = 'Authorization';
-  const header = `${username || ''}:${password || ''}`;
-  // @ts-expect-error -- TSCONVERSION appears to be a genuine error
+  const header = `${username ?? ''}:${password ?? ''}`;
   const authString = Buffer.from(header, encoding).toString('base64');
   const value = `Basic ${authString}`;
   const requestHeader: RequestHeader = {
diff --git a/packages/insomnia/src/network/o-auth-2/get-token.ts b/packages/insomnia/src/network/o-auth-2/get-token.ts
index 3a30eaa55..1bf82db1c 100644
--- a/packages/insomnia/src/network/o-auth-2/get-token.ts
+++ b/packages/insomnia/src/network/o-auth-2/get-token.ts
@@ -159,7 +159,7 @@ export const getOAuth2Token = async (
       ...insertAuthKeyIf('client_secret', authentication.clientSecret),
     ];
   } else {
-    headers.push(getBasicAuthHeader(authentication.clientId, authentication.clientSecret));
+    headers.push(getBasicAuthHeader(encodeURIComponent(authentication.clientId ?? ''), encodeURIComponent(authentication.clientSecret ?? '')));
   }
 
   const response = await sendAccessTokenRequest(requestId, authentication, params, headers);