diff --git a/apps/browser/src/background/main.background.ts b/apps/browser/src/background/main.background.ts
index 2d1da8510c1..e4fbe1f4edf 100644
--- a/apps/browser/src/background/main.background.ts
+++ b/apps/browser/src/background/main.background.ts
@@ -578,7 +578,7 @@ export default class MainBackground {
           "ephemeral",
           "bitwarden-ephemeral",
         );
-        await sessionStorage.save("session-key", derivedKey);
+        await sessionStorage.save("session-key", derivedKey.toJSON());
         return derivedKey;
       });