diff --git a/ts/sql/migrations/50-fix-messages-unread-index.ts b/ts/sql/migrations/50-fix-messages-unread-index.ts
new file mode 100644
index 000000000..d1fc05a81
--- /dev/null
+++ b/ts/sql/migrations/50-fix-messages-unread-index.ts
@@ -0,0 +1,32 @@
+// Copyright 2021 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+import type { Database } from 'better-sqlite3';
+
+import type { LoggerType } from '../../types/Logging';
+
+export default function updateToSchemaVersion50(
+  currentVersion: number,
+  db: Database,
+  logger: LoggerType
+): void {
+  if (currentVersion >= 50) {
+    return;
+  }
+
+  db.transaction(() => {
+    db.exec(
+      `
+      DROP INDEX messages_unread;
+
+      -- Note: here we move to the modern isStory/storyId fields and add received_at/sent_at.
+      CREATE INDEX messages_unread ON messages
+        (conversationId, readStatus, isStory, storyId, received_at, sent_at) WHERE readStatus IS NOT NULL;
+      `
+    );
+
+    db.pragma('user_version = 50');
+  })();
+
+  logger.info('updateToSchemaVersion50: success!');
+}
diff --git a/ts/sql/migrations/index.ts b/ts/sql/migrations/index.ts
index 0cad9e2e0..f0a03c4f2 100644
--- a/ts/sql/migrations/index.ts
+++ b/ts/sql/migrations/index.ts
@@ -25,6 +25,7 @@ import updateToSchemaVersion46 from './46-optimize-stories';
 import updateToSchemaVersion47 from './47-further-optimize';
 import updateToSchemaVersion48 from './48-fix-user-initiated-index';
 import updateToSchemaVersion49 from './49-fix-preview-index';
+import updateToSchemaVersion50 from './50-fix-messages-unread-index';
 
 function updateToSchemaVersion1(
   currentVersion: number,
@@ -1913,6 +1914,7 @@ export const SCHEMA_VERSIONS = [
   updateToSchemaVersion47,
   updateToSchemaVersion48,
   updateToSchemaVersion49,
+  updateToSchemaVersion50,
 ];
 
 export function updateSchema(db: Database, logger: LoggerType): void {
diff --git a/ts/test-node/sql_migrations_test.ts b/ts/test-node/sql_migrations_test.ts
index a47dec04c..c2b67bc95 100644
--- a/ts/test-node/sql_migrations_test.ts
+++ b/ts/test-node/sql_migrations_test.ts
@@ -1324,4 +1324,31 @@ describe('SQL migrations test', () => {
       assert.notInclude(details, 'SCAN');
     });
   });
+
+  describe('updateToSchemaVersion49', () => {
+    it('creates usable index for messages_unread', () => {
+      updateToVersion(50);
+
+      const details = db
+        .prepare(
+          `
+          EXPLAIN QUERY PLAN
+          SELECT * FROM messages WHERE
+            conversationId = 'conversation' AND
+            readStatus = 'something' AND
+            isStory IS 0 AND
+            storyId IS NULL
+          ORDER BY received_at ASC, sent_at ASC
+          LIMIT 1;
+        `
+        )
+        .all()
+        .map(({ detail }) => detail)
+        .join('\n');
+
+      assert.include(details, 'USING INDEX messages_unread');
+      assert.notInclude(details, 'TEMP B-TREE');
+      assert.notInclude(details, 'SCAN');
+    });
+  });
 });