diff --git a/spec/unit/rust-crypto/rust-crypto.spec.ts b/spec/unit/rust-crypto/rust-crypto.spec.ts
index fef825582..1a1ff5525 100644
--- a/spec/unit/rust-crypto/rust-crypto.spec.ts
+++ b/spec/unit/rust-crypto/rust-crypto.spec.ts
@@ -304,6 +304,56 @@ describe("initRustCrypto", () => {
             }
         }, 10000);
 
+        it("migrates data from a legacy crypto store when secret are not encrypted", async () => {
+            const PICKLE_KEY = "pickle1234";
+            const legacyStore = new MemoryCryptoStore();
+
+            // It's possible for old sessions to directly store the secrets as raw UInt8Array,
+            // so we need to support that in the migration code.
+            // See https://github.com/matrix-org/matrix-js-sdk/commit/c81f11df0afd4d0da3b088892745ae2f8ba1c4a7
+            async function storeSecretKeyInClear(type: string, key: Uint8Array, store: CryptoStore) {
+                // @ts-ignore The API to store raw UInt8Array does not exist anymore, so we need that for this test.
+                store.privateKeys[type as keyof SecretStorePrivateKeys] = key;
+            }
+
+            // Populate the legacy store with some test data
+            const storeSecretKey = (type: string, key: string) =>
+                storeSecretKeyInClear(type, new TextEncoder().encode(key), legacyStore);
+
+            await legacyStore.storeAccount({}, "not a real account");
+            await storeSecretKey("master", "master key");
+            await storeSecretKey("self_signing", "ssk");
+            await storeSecretKey("user_signing", "usk");
+
+            fetchMock.get("path:/_matrix/client/v3/room_keys/version", 404);
+
+            function legacyMigrationProgressListener(progress: number, total: number): void {
+                logger.log(`migrated ${progress} of ${total}`);
+            }
+
+            await initRustCrypto({
+                logger,
+                http: makeMatrixHttpApi(),
+                userId: TEST_USER,
+                deviceId: TEST_DEVICE_ID,
+                secretStorage: {} as ServerSideSecretStorage,
+                cryptoCallbacks: {} as CryptoCallbacks,
+                storePrefix: "storePrefix",
+                storePassphrase: "storePassphrase",
+                legacyCryptoStore: legacyStore,
+                legacyPickleKey: PICKLE_KEY,
+                legacyMigrationProgressListener,
+            });
+
+            const data = mocked(Migration.migrateBaseData).mock.calls[0][0];
+            expect(data.pickledAccount).toEqual("not a real account");
+            expect(data.userId!.toString()).toEqual(TEST_USER);
+            expect(data.deviceId!.toString()).toEqual(TEST_DEVICE_ID);
+            expect(atob(data.privateCrossSigningMasterKey!)).toEqual("master key");
+            expect(atob(data.privateCrossSigningUserSigningKey!)).toEqual("usk");
+            expect(atob(data.privateCrossSigningSelfSigningKey!)).toEqual("ssk");
+        });
+
         it("handles megolm sessions with no `keysClaimed`", async () => {
             const legacyStore = new MemoryCryptoStore();
             legacyStore.storeAccount({}, "not a real account");
diff --git a/src/rust-crypto/libolm_migration.ts b/src/rust-crypto/libolm_migration.ts
index ef9e6697a..2738f88f6 100644
--- a/src/rust-crypto/libolm_migration.ts
+++ b/src/rust-crypto/libolm_migration.ts
@@ -27,6 +27,7 @@ import { CrossSigningKeyInfo, Curve25519AuthData } from "../crypto-api";
 import { RustCrypto } from "./rust-crypto";
 import { KeyBackupInfo } from "../crypto-api/keybackup";
 import { sleep } from "../utils";
+import { encodeBase64 } from "../base64";
 
 /**
  * Determine if any data needs migrating from the legacy store, and do so.
@@ -400,19 +401,20 @@ async function getAndDecryptCachedSecretKey(
     legacyPickleKey: Uint8Array,
     name: string,
 ): Promise<string | undefined> {
-    let encodedKey: IEncryptedPayload | null = null;
-
-    await legacyStore.doTxn("readonly", "account", (txn) => {
-        legacyStore.getSecretStorePrivateKey(
-            txn,
-            (k) => {
-                encodedKey = k as IEncryptedPayload | null;
-            },
-            name as keyof SecretStorePrivateKeys,
-        );
+    const key = await new Promise<any>((resolve) => {
+        legacyStore.doTxn("readonly", [IndexedDBCryptoStore.STORE_ACCOUNT], (txn) => {
+            legacyStore.getSecretStorePrivateKey(txn, resolve, name as keyof SecretStorePrivateKeys);
+        });
     });
 
-    return encodedKey === null ? undefined : await decryptAES(encodedKey, legacyPickleKey, name);
+    if (key && key.ciphertext && key.iv && key.mac) {
+        return await decryptAES(key as IEncryptedPayload, legacyPickleKey, name);
+    } else if (key instanceof Uint8Array) {
+        // This is a legacy backward compatibility case where the key was stored in clear.
+        return encodeBase64(key);
+    } else {
+        return undefined;
+    }
 }
 
 /**