diff --git a/packages/lib/services/e2ee/utils.test.ts b/packages/lib/services/e2ee/utils.test.ts
index 95dfe048953..4a2191c064f 100644
--- a/packages/lib/services/e2ee/utils.test.ts
+++ b/packages/lib/services/e2ee/utils.test.ts
@@ -1,4 +1,4 @@
-import { afterAllCleanUp, setupDatabaseAndSynchronizer, switchClient, encryptionService } from '../../testing/test-utils';
+import { afterAllCleanUp, setupDatabaseAndSynchronizer, switchClient, encryptionService, expectNotThrow } from '../../testing/test-utils';
 import MasterKey from '../../models/MasterKey';
 import { showMissingMasterKeyMessage } from './utils';
 import { localSyncInfo, setMasterKeyEnabled } from '../synchronizer/syncInfoUtils';
@@ -34,6 +34,8 @@ describe('e2ee/utils', function() {
 		setMasterKeyEnabled(mk2.id, true);
 		expect(showMissingMasterKeyMessage(localSyncInfo(), [mk1.id, mk2.id])).toBe(true);
 
+		await expectNotThrow(async () => showMissingMasterKeyMessage(localSyncInfo(), ['not_downloaded_yet']));
+
 		const syncInfo = localSyncInfo();
 		syncInfo.masterKeys = [];
 		expect(showMissingMasterKeyMessage(syncInfo, [mk1.id, mk2.id])).toBe(false);
diff --git a/packages/lib/services/e2ee/utils.ts b/packages/lib/services/e2ee/utils.ts
index 7280e5f1d94..9df4e570136 100644
--- a/packages/lib/services/e2ee/utils.ts
+++ b/packages/lib/services/e2ee/utils.ts
@@ -98,6 +98,14 @@ export function showMissingMasterKeyMessage(syncInfo: SyncInfo, notLoadedMasterK
 
 	for (let i = notLoadedMasterKeys.length - 1; i >= 0; i--) {
 		const mk = syncInfo.masterKeys.find(mk => mk.id === notLoadedMasterKeys[i]);
+
+		// A "notLoadedMasterKey" is a key that either doesn't exist or for
+		// which a password hasn't been set yet. For the purpose of this
+		// function, we only want to notify the user about unset passwords.
+		// Master keys that haven't been downloaded yet should normally be
+		// downloaded at some point.
+		// https://github.com/laurent22/joplin/issues/5391
+		if (!mk) continue;
 		if (!masterKeyEnabled(mk)) notLoadedMasterKeys.pop();
 	}