diff --git a/src/matrix-utils.ts b/src/matrix-utils.ts
index e3617c5..7f98f9f 100644
--- a/src/matrix-utils.ts
+++ b/src/matrix-utils.ts
@@ -48,7 +48,7 @@ export async function initClient(
   window.OLM_OPTIONS = {};
   await Olm.init({ locateFile: () => olmWasmPath });
 
-  let indexedDB;
+  let indexedDB: IDBFactory;
 
   try {
     indexedDB = window.indexedDB;