diff --git a/src/services.js b/src/services.js
index 50658b3a4..6271cc44a 100644
--- a/src/services.js
+++ b/src/services.js
@@ -1502,13 +1502,14 @@ const SERVICES = {
         name: 'Mail',
         status: containerStatus.bind(null, 'mail'),
         restart: () => mailServer.restart(),
+        // delayed loading because of esm modules
         get defaultMemoryLimit() { return mailServer.DEFAULT_MEMORY_LIMIT; }
     },
     mongodb: {
         name: 'MongoDB',
         status: statusMongodb,
         restart: restartMongodb,
-        defaultMemoryLimit: (1 + Math.round(os.totalmem()/(1024*1024*1024)/4)) * 256 * 1024 * 1024
+        defaultMemoryLimit: Math.max(2 * 1024 * 1024 * 1024, (1 + Math.round(os.totalmem()/(1024*1024*1024)/4)) * 256 * 1024 * 1024)
     },
     mysql: {
         name: 'MySQL',