diff --git a/src/background.ts b/src/background.ts
index 5135fdc6..04da8de2 100644
--- a/src/background.ts
+++ b/src/background.ts
@@ -14,7 +14,8 @@ function reloadSeqtaPages() {
   result.then(open, console.error);
 }
 
-type MessageSender = (_?: unknown) => void;
+/** Callback for sending a response back to the message sender */
+type MessageSender = { (response?: unknown): void };
 
 function handleFetchThemes(request: any, sendResponse: MessageSender): boolean {
   const { token } = request;
@@ -166,7 +167,8 @@ function handleCloudFavorite(request: any, sendResponse: MessageSender): boolean
   return true;
 }
 
-type MessageHandler = (_req: any, _res: MessageSender) => boolean | void;
+/** Handler for a message type; receives request and sendResponse callback */
+type MessageHandler = { (request: any, sendResponse: MessageSender): boolean | void };
 
 const MESSAGE_HANDLERS: Record<string, MessageHandler> = {
   reloadTabs: () => reloadSeqtaPages(),
diff --git a/src/seqta/utils/CloudAuth.ts b/src/seqta/utils/CloudAuth.ts
index ccff2f5a..ff4f15f8 100644
--- a/src/seqta/utils/CloudAuth.ts
+++ b/src/seqta/utils/CloudAuth.ts
@@ -24,7 +24,8 @@ export type CloudAuthState = {
   user: CloudUser | null;
 };
 
-type Listener = (_: CloudAuthState) => void;
+/** Callback invoked when auth state changes */
+type Listener = { (state: CloudAuthState): void };
 
 class CloudAuthService {
   private static instance: CloudAuthService;