diff --git a/src/crypto/algorithms/megolm.js b/src/crypto/algorithms/megolm.js
index 95cf43e3e..89221fac1 100644
--- a/src/crypto/algorithms/megolm.js
+++ b/src/crypto/algorithms/megolm.js
@@ -629,9 +629,7 @@ MegolmEncryption.prototype.reshareKeyWithDevice = async function(
 
     await olmlib.ensureOlmSessionsForDevices(
         this._olmDevice, this._baseApis, {
-            [userId]: {
-                [device.deviceId]: device,
-            },
+            [userId]: [device],
         },
     );