diff --git a/src/uas/QGCUASFileManager.cc b/src/uas/QGCUASFileManager.cc
index 41b726d993f7f52873cf71bee87b5490470143b4..3728c9690602e96cfb6a9feff5fdf9372eed9995 100644
--- a/src/uas/QGCUASFileManager.cc
+++ b/src/uas/QGCUASFileManager.cc
@@ -471,15 +471,19 @@ void QGCUASFileManager::_clearAckTimeout(void)
 /// @brief Called when ack timeout timer fires
 void QGCUASFileManager::_ackTimeout(void)
 {
-    _emitErrorMessage(tr("Timeout waiting for ack"));
+    // Make sure to set _currentOperation state before emitting error message. Code may respond
+    // to error message signal by sending another command, which will fail if state is not back
+    // to idle. FileView UI works this way with the List command.
 
     switch (_currentOperation) {
         case kCORead:
             _currentOperation = kCOAck;
+            _emitErrorMessage(tr("Timeout waiting for ack: Sending Terminate command"));
             _sendTerminateCommand();
             break;
         default:
             _currentOperation = kCOIdle;
+            _emitErrorMessage(tr("Timeout waiting for ack"));
             break;
     }
 }
diff --git a/src/ui/QGCUASFileView.cc b/src/ui/QGCUASFileView.cc
index 0635b4c0534792e5a11c24b48a69c0c7b83bcad5..3164040d3ac6a9c12b2f31e8e9df4d76a4075fc7 100644
--- a/src/ui/QGCUASFileView.cc
+++ b/src/ui/QGCUASFileView.cc
@@ -40,7 +40,9 @@ QGCUASFileView::QGCUASFileView(QWidget *parent, QGCUASFileManager *manager) :
     Q_ASSERT(success);
     success = connect(_ui.treeWidget, SIGNAL(currentItemChanged(QTreeWidgetItem*, QTreeWidgetItem*)), this, SLOT(_currentItemChanged(QTreeWidgetItem*, QTreeWidgetItem*)));
     Q_ASSERT(success);
-    Q_UNUSED(success);
+    success = connect(&_listCompleteTimer, SIGNAL(timeout()), this, SLOT(_listCompleteTimeout()));
+    Q_ASSERT(success);
+    Q_UNUSED(success);    // Silence retail unused variable error
 }
 
 void QGCUASFileView::_downloadFiles(void)
@@ -88,8 +90,7 @@ void QGCUASFileView::_refreshTree(void)
     // Don't queue up more than once
     _ui.listFilesButton->setEnabled(false);
 
-    qDebug() << "List: /";
-    _manager->listDirectory("/");
+    _requestDirectoryList("/");
 }
 
 void QGCUASFileView::_treeStatusMessage(const QString& msg)
@@ -128,6 +129,8 @@ void QGCUASFileView::_treeErrorMessage(const QString& msg)
 
 void QGCUASFileView::_listComplete(void)
 {
+    _clearListCompleteTimeout();
+    
     // Walk the current items, traversing down into directories
     
 Again:
@@ -159,8 +162,7 @@ Again:
             QTreeWidgetItem* item = _walkItemStack[i];
             dir.append("/" + item->text(0));
         }
-        qDebug() << "List:" << dir;
-        _manager->listDirectory(dir);
+        _requestDirectoryList(dir);
     } else {
         // We have run out of items at the this level, pop the stack and keep going at that level
         _walkIndexStack.removeLast();
@@ -192,3 +194,30 @@ void QGCUASFileView::_currentItemChanged(QTreeWidgetItem* current, QTreeWidgetIt
     Q_UNUSED(previous);
     _ui.downloadButton->setEnabled(current ? (current->type() == _typeFile) : false);
 }
+
+void QGCUASFileView::_setupListCompleteTimeout(void)
+{
+    Q_ASSERT(!_listCompleteTimer.isActive());
+    
+    _listCompleteTimer.setSingleShot(true);
+    _listCompleteTimer.start(_listCompleteTimerTimeoutMsecs);
+}
+
+void QGCUASFileView::_clearListCompleteTimeout(void)
+{
+    Q_ASSERT(_listCompleteTimer.isActive());
+    
+    _listCompleteTimer.stop();
+}
+
+void QGCUASFileView::_listCompleteTimeout(void)
+{
+    _treeErrorMessage(tr("Timeout waiting for listComplete signal"));
+}
+
+void QGCUASFileView::_requestDirectoryList(const QString& dir)
+{
+    qDebug() << "List:" << dir;
+    _setupListCompleteTimeout();
+    _manager->listDirectory(dir);
+}
diff --git a/src/ui/QGCUASFileView.h b/src/ui/QGCUASFileView.h
index 0b33e5b3b35e7b1f9b15044546dcecbd8a9a382e..102491587650b3af93d496b23856c0748122ceae 100644
--- a/src/ui/QGCUASFileView.h
+++ b/src/ui/QGCUASFileView.h
@@ -48,12 +48,20 @@ private slots:
     void _listComplete(void);
     void _downloadStatusMessage(const QString& msg);
     void _currentItemChanged(QTreeWidgetItem* current, QTreeWidgetItem* previous);
+    void _listCompleteTimeout(void);
 
 private:
+    void _setupListCompleteTimeout(void);
+    void _clearListCompleteTimeout(void);
+    void _requestDirectoryList(const QString& dir);
+
     static const int        _typeFile = QTreeWidgetItem::UserType + 1;
     static const int        _typeDir = QTreeWidgetItem::UserType + 2;
     static const int        _typeError = QTreeWidgetItem::UserType + 3;
     
+    QTimer                  _listCompleteTimer;                     ///> Used to signal a timeout waiting for a listComplete signal
+    static const int        _listCompleteTimerTimeoutMsecs = 5000;  ///> Timeout in msecs for listComplete timer
+    
     QList<int>              _walkIndexStack;
     QList<QTreeWidgetItem*> _walkItemStack;
     Ui::QGCUASFileView      _ui;