diff --git a/src/apptaskmanager.js b/src/apptaskmanager.js
index d72fb54ce..bfbe3c5a1 100644
--- a/src/apptaskmanager.js
+++ b/src/apptaskmanager.js
@@ -1,7 +1,7 @@
 'use strict';
 
 exports = module.exports = {
-    scheduleTask: scheduleTask
+    scheduleTask
 };
 
 let assert = require('assert'),
@@ -12,6 +12,7 @@ let assert = require('assert'),
     safe = require('safetydance'),
     path = require('path'),
     paths = require('./paths.js'),
+    scheduler = require('./scheduler.js'),
     sftp = require('./sftp.js'),
     tasks = require('./tasks.js');
 
@@ -69,6 +70,8 @@ function scheduleTask(appId, taskId, callback) {
 
     if (!fs.existsSync(path.dirname(logFile))) safe.fs.mkdirSync(path.dirname(logFile)); // ensure directory
 
+    scheduler.suspendJobs(appId);
+
     // TODO: set memory limit for app backup task
     tasks.startTask(taskId, { logFile, timeout: 20 * 60 * 60 * 1000 /* 20 hours */, nice: 15 }, function (error, result) {
         callback(error, result);
@@ -77,9 +80,8 @@ function scheduleTask(appId, taskId, callback) {
         locker.unlock(locker.OP_APPTASK); // unlock event will trigger next task
 
         // post app task hooks
-        sftp.rebuild(function (error) {
-            if (error) debug('Unable to rebuild sftp:', error);
-        });
+        sftp.rebuild(error => { if (error) debug('Unable to rebuild sftp:', error); });
+        scheduler.resumeJobs(appId);
     });
 }
 
diff --git a/src/scheduler.js b/src/scheduler.js
index a952d87de..080bf15ce 100644
--- a/src/scheduler.js
+++ b/src/scheduler.js
@@ -1,7 +1,9 @@
 'use strict';
 
 exports = module.exports = {
-    sync: sync
+    sync,
+    suspendJobs,
+    resumeJobs
 };
 
 let apps = require('./apps.js'),
@@ -15,8 +17,18 @@ let apps = require('./apps.js'),
     _ = require('underscore');
 
 // appId -> { containerId, schedulerConfig (manifest), cronjobs }
-var gState = { };
+let gState = { };
+let gSuspendedAppIds = new Set(); // suspended because some apptask is running
 
+function suspendJobs(appId) {
+    debug(`suspendJobs: ${appId}`);
+    gSuspendedAppIds.add(appId);
+}
+
+function resumeJobs(appId) {
+    debug(`resumeJobs: ${appId}`);
+    gSuspendedAppIds.delete(appId);
+}
 
 function runTask(appId, taskName, callback) {
     assert.strictEqual(typeof appId, 'string');
@@ -26,6 +38,8 @@ function runTask(appId, taskName, callback) {
     const JOB_MAX_TIME = 30 * 60 * 1000; // 30 minutes
     const containerName = `${appId}-${taskName}`;
 
+    if (gSuspendedAppIds.has(appId)) return callback();
+
     apps.get(appId, function (error, app) {
         if (error) return callback(error);