diff --git a/src/rust-crypto/rust-crypto.ts b/src/rust-crypto/rust-crypto.ts
index e516e199f..0d5b4a4f3 100644
--- a/src/rust-crypto/rust-crypto.ts
+++ b/src/rust-crypto/rust-crypto.ts
@@ -319,7 +319,7 @@ export class RustCrypto implements CryptoBackend {
     private async receiveSyncChanges({
         events,
         oneTimeKeysCounts = new Map<string, number>(),
-        unusedFallbackKeys = new Set<string>(),
+        unusedFallbackKeys,
         devices = new RustSdkCryptoJs.DeviceLists(),
     }: {
         events?: IToDeviceEvent[];