diff --git a/src/ClientContext.tsx b/src/ClientContext.tsx
index 68676ad5..503c3f8f 100644
--- a/src/ClientContext.tsx
+++ b/src/ClientContext.tsx
@@ -101,12 +101,15 @@ export const ClientProvider: FC<Props> = ({ children }) => {
           const { user_id, device_id, access_token, passwordlessUser } =
             session;
 
-          const client = await initClient({
-            baseUrl: defaultHomeserver,
-            accessToken: access_token,
-            userId: user_id,
-            deviceId: device_id,
-          });
+          const client = await initClient(
+            {
+              baseUrl: defaultHomeserver,
+              accessToken: access_token,
+              userId: user_id,
+              deviceId: device_id,
+            },
+            true
+          );
           /* eslint-enable camelcase */
 
           return { client, isPasswordlessUser: passwordlessUser };
diff --git a/src/auth/useInteractiveLogin.ts b/src/auth/useInteractiveLogin.ts
index 6379c67c..9ffa7ba6 100644
--- a/src/auth/useInteractiveLogin.ts
+++ b/src/auth/useInteractiveLogin.ts
@@ -57,12 +57,15 @@ export const useInteractiveLogin = () =>
       passwordlessUser: false,
     };
 
-    const client = await initClient({
-      baseUrl: defaultHomeserver,
-      accessToken: access_token,
-      userId: user_id,
-      deviceId: device_id,
-    });
+    const client = await initClient(
+      {
+        baseUrl: defaultHomeserver,
+        accessToken: access_token,
+        userId: user_id,
+        deviceId: device_id,
+      },
+      false
+    );
     /* eslint-enable camelcase */
 
     return [client, session];
diff --git a/src/auth/useInteractiveRegistration.ts b/src/auth/useInteractiveRegistration.ts
index af611f9d..8b8647a0 100644
--- a/src/auth/useInteractiveRegistration.ts
+++ b/src/auth/useInteractiveRegistration.ts
@@ -90,12 +90,15 @@ export const useInteractiveRegistration = (): [
       const { user_id, access_token, device_id } =
         (await interactiveAuth.attemptAuth()) as any;
 
-      const client = await initClient({
-        baseUrl: defaultHomeserver,
-        accessToken: access_token,
-        userId: user_id,
-        deviceId: device_id,
-      });
+      const client = await initClient(
+        {
+          baseUrl: defaultHomeserver,
+          accessToken: access_token,
+          userId: user_id,
+          deviceId: device_id,
+        },
+        false
+      );
 
       await client.setDisplayName(displayName);
 
diff --git a/src/matrix-utils.ts b/src/matrix-utils.ts
index 1a1a2ea6..3e576e78 100644
--- a/src/matrix-utils.ts
+++ b/src/matrix-utils.ts
@@ -24,6 +24,19 @@ export const defaultHomeserver =
 
 export const defaultHomeserverHost = new URL(defaultHomeserver).host;
 
+export class CryptoStoreIntegrityError extends Error {
+  constructor() {
+    super("Crypto store data was expected, but none was found");
+  }
+}
+
+const SYNC_STORE_NAME = "element-call-sync";
+// Note that the crypto store name has changed from previous versions
+// deliberately in order to force a logout for all users due to
+// https://github.com/vector-im/element-call/issues/464
+// (It's a good opportunity to make the database names consistent.)
+const CRYPTO_STORE_NAME = "element-call-crypto";
+
 function waitForSync(client: MatrixClient) {
   return new Promise<void>((resolve, reject) => {
     const onSync = (
@@ -43,8 +56,18 @@ function waitForSync(client: MatrixClient) {
   });
 }
 
+/**
+ * Initialises and returns a new Matrix Client
+ * If true is passed for the 'restore' parameter, a check will be made
+ * to ensure that corresponding crypto data is stored and recovered.
+ * If the check fails, CryptoStoreIntegrityError will be thrown.
+ * @param clientOptions Object of options passed through to the client
+ * @param restore Whether the session is being restored from storage
+ * @returns The MatrixClient instance
+ */
 export async function initClient(
-  clientOptions: ICreateClientOpts
+  clientOptions: ICreateClientOpts,
+  restore: boolean
 ): Promise<MatrixClient> {
   // TODO: https://gitlab.matrix.org/matrix-org/olm/-/issues/10
   window.OLM_OPTIONS = {};
@@ -62,17 +85,45 @@ export async function initClient(
     storeOpts.store = new IndexedDBStore({
       indexedDB: window.indexedDB,
       localStorage,
-      dbName: "element-call-sync",
+      dbName: SYNC_STORE_NAME,
       workerFactory: () => new IndexedDBWorker(),
     });
   } else if (localStorage) {
     storeOpts.store = new MemoryStore({ localStorage });
   }
 
+  // Check whether we have crypto data store. If we are restoring a session
+  // from storage then we will have started the crypto store and therefore
+  // have generated keys for that device, so if we can't recover those keys,
+  // we must not continue or we'll generate new keys and anyone who saw our
+  // previous keys will not accept our new key.
+  // It's worth mentioning here that if support for indexeddb or localstorage
+  // appears or disappears between sessions (it happens) then the failure mode
+  // here will be that we'll try a different store, not find crypto data and
+  // fail to restore the session. An alternative would be to continue using
+  // whatever we were using before, but that could be confusing since you could
+  // enable indexeddb and but the app would still not be using it.
+  if (restore) {
+    if (indexedDB) {
+      const cryptoStoreExists = await IndexedDBCryptoStore.exists(
+        indexedDB,
+        CRYPTO_STORE_NAME
+      );
+      if (!cryptoStoreExists) throw new CryptoStoreIntegrityError();
+    } else if (localStorage) {
+      if (!LocalStorageCryptoStore.exists(localStorage))
+        throw new CryptoStoreIntegrityError();
+    } else {
+      // if we get here then we're using the memory store, which cannot
+      // possibly have remembered a session, so it's an error.
+      throw new CryptoStoreIntegrityError();
+    }
+  }
+
   if (indexedDB) {
     storeOpts.cryptoStore = new IndexedDBCryptoStore(
       indexedDB,
-      "matrix-js-sdk:crypto"
+      CRYPTO_STORE_NAME
     );
   } else if (localStorage) {
     storeOpts.cryptoStore = new LocalStorageCryptoStore(localStorage);