diff --git a/apps/machine/electron/main.ts b/apps/machine/electron/main.ts
index 1b6c41e..46696ab 100644
--- a/apps/machine/electron/main.ts
+++ b/apps/machine/electron/main.ts
@@ -119,7 +119,9 @@ ipcMain.handle('get-config', () => {
     validatorDevice: process.env.VITE_LAMASSU_VALIDATOR_DEVICE,
     dispenserDevice: process.env.VITE_LAMASSU_DISPENSER_DEVICE,
     cassettes: process.env.VITE_LAMASSU_CASSETTES,
-    allowMockFallback: process.env.VITE_ALLOW_MOCK_FALLBACK === 'true',
+    // SECURITY: In production (packaged app), mock fallback is always disabled.
+    // Only allow it in development mode, and only when explicitly opted in via env.
+    allowMockFallback: isDev && process.env.VITE_ALLOW_MOCK_FALLBACK === 'true',
   }
 })