diff --git a/packages/webapp/webapp.d.ts b/packages/webapp/webapp.d.ts
index e13bb9ccf0..48aa79c618 100644
--- a/packages/webapp/webapp.d.ts
+++ b/packages/webapp/webapp.d.ts
@@ -39,6 +39,7 @@ export declare module WebApp {
   function addRuntimeConfigHook(callback: RuntimeConfigHookCallback): void;
   function decodeRuntimeConfig(rtimeConfigString: string): unknown;
   function encodeRuntimeConfig(rtimeConfig: unknown): string;
+  function addHtmlAttributeHook(hook: Function): void;
 }
 
 export declare module WebAppInternals {