diff --git a/CHANGES b/CHANGES
index 01da355f4..9f4ee6036 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1661,4 +1661,5 @@
 * Check disk space before various operations like install, update, backup etc
 * Collect per app du information
 * Set Cloudron specific UA for healthchecks
+* Show message why an app task is 'pending'
 
diff --git a/src/apps.js b/src/apps.js
index d9c6c4a4c..d734809af 100644
--- a/src/apps.js
+++ b/src/apps.js
@@ -1182,7 +1182,7 @@ function uninstall(appId, auditSource, callback) {
     assert.strictEqual(typeof auditSource, 'object');
     assert.strictEqual(typeof callback, 'function');
 
-    debug('Will uninstall app with id:%s', appId);
+    debug(`Will uninstall app with id : ${appId}`);
 
     get(appId, function (error, app) {
         if (error) return callback(error);
@@ -1194,7 +1194,7 @@ function uninstall(appId, auditSource, callback) {
             if (error && error.reason === AppstoreError.EXTERNAL_ERROR) return callback(new AppsError(AppsError.EXTERNAL_ERROR, error.message));
             if (error) return callback(new AppsError(AppsError.INTERNAL_ERROR, error));
 
-            appdb.setInstallationCommand(appId, appdb.ISTATE_PENDING_UNINSTALL, function (error) {
+            appdb.update(appId, { installationState: appdb.ISTATE_PENDING_UNINSTALL }, function (error) {
                 if (error && error.reason === DatabaseError.NOT_FOUND) return callback(new AppsError(AppsError.NOT_FOUND, 'No such app'));
                 if (error) return callback(new AppsError(AppsError.INTERNAL_ERROR, error));
 
diff --git a/src/apptaskmanager.js b/src/apptaskmanager.js
index f77d00490..e8d350703 100644
--- a/src/apptaskmanager.js
+++ b/src/apptaskmanager.js
@@ -22,6 +22,14 @@ let gPendingTasks = [ ];
 const TASK_CONCURRENCY = 3;
 const NOOP_CALLBACK = function (error) { if (error) debug(error); };
 
+function waitText(lockOperation) {
+    if (lockOperation === locker.OP_BOX_UPDATE) return 'Waiting for Cloudron to finish updating. See the Settings view';
+    if (lockOperation === locker.OP_PLATFORM_START) return 'Waiting for Cloudron to initialize';
+    if (lockOperation === locker.OP_FULL_BACKUP) return 'Wait for Cloudron to finish backup. See the Backups view';
+
+    return ''; // cannot happen
+}
+
 // callback is called when task is finished
 function scheduleTask(appId, taskId, callback) {
     assert.strictEqual(typeof appId, 'string');
@@ -34,6 +42,7 @@ function scheduleTask(appId, taskId, callback) {
 
     if (Object.keys(gActiveTasks).length >= TASK_CONCURRENCY) {
         debug(`Reached concurrency limit, queueing task id ${taskId}`);
+        tasks.update(taskId, { percent: 0, message: 'Waiting for other app tasks to complete' }, NOOP_CALLBACK);
         gPendingTasks.push({ appId, taskId, callback });
         return;
     }
@@ -41,7 +50,8 @@ function scheduleTask(appId, taskId, callback) {
     var lockError = locker.recursiveLock(locker.OP_APPTASK);
 
     if (lockError) {
-        debug(`Locked for another operation, queueing task id ${taskId}`);
+        debug(`Could not get lock. ${lockError.message}, queueing task id ${taskId}`);
+        tasks.update(taskId, { percent: 0, message: waitText(lockError.operation) }, NOOP_CALLBACK);
         gPendingTasks.push({ appId, taskId, callback });
         return;
     }
diff --git a/src/locker.js b/src/locker.js
index c40db92ed..369e355c3 100644
--- a/src/locker.js
+++ b/src/locker.js
@@ -22,7 +22,11 @@ Locker.prototype.OP_APPTASK = 'apptask';
 Locker.prototype.lock = function (operation) {
     assert.strictEqual(typeof operation, 'string');
 
-    if (this._operation !== null) return new Error('Already locked for ' + this._operation);
+    if (this._operation !== null) {
+        let error = new Error(`Locked for ${this._operation}`);
+        error.operation = this._operation;
+        return error;
+    }
 
     this._operation = operation;
     ++this._lockDepth;