diff --git a/apps/micropolis/src/lib/citySaveFormat.test.ts b/apps/micropolis/src/lib/citySaveFormat.test.ts
new file mode 100644
index 00000000..4506a8e4
--- /dev/null
+++ b/apps/micropolis/src/lib/citySaveFormat.test.ts
@@ -0,0 +1,19 @@
+import { describe, it, expect } from 'vitest';
+import { loadMicropolisMainModule } from './wasm/node';
+import { createNoopJsCallback } from './wasm/callbacks';
+
+describe('city save format', () => {
+	it('writes a city file the same size as the one it loaded', async () => {
+		const engine = await loadMicropolisMainModule();
+		const micropolis = new engine.Micropolis();
+		micropolis.setCallback(createNoopJsCallback(engine), {});
+		micropolis.init();
+		const city = '/cities/haight.cty';
+		expect(micropolis.loadCity(city)).toBe(true);
+
+		micropolis.saveCityAs('/saved.cty');
+		expect(engine.FS_readFile('/saved.cty').length).toBe(engine.FS_readFile(city).length);
+
+		micropolis.delete();
+	});
+});
diff --git a/packages/micropolis-engine/src/fileio.cpp b/packages/micropolis-engine/src/fileio.cpp
index 30e91a04..5b51dd64 100644
--- a/packages/micropolis-engine/src/fileio.cpp
+++ b/packages/micropolis-engine/src/fileio.cpp
@@ -455,8 +455,7 @@ bool Micropolis::saveFile(const std::string &filename)
          * linear index x * WORLD_H + y. This is column-major relative to city
          * coordinates, and is the same order exposed to JavaScript/WASM tools.
          */
-        save_short(((short *)&map[0][0]), WORLD_W * WORLD_H, f) &&
-        save_short(((short *)&mop[0][0]), WORLD_W * WORLD_H, f);
+        save_short(((short *)&map[0][0]), WORLD_W * WORLD_H, f);
 
     fclose(f);