diff --git a/src/gui/folder.cpp b/src/gui/folder.cpp
index 8967b1f6c9f6a..a0458ea632a9a 100644
--- a/src/gui/folder.cpp
+++ b/src/gui/folder.cpp
@@ -1302,6 +1302,19 @@ QString Folder::fileFromLocalPath(const QString &localPath) const
 void Folder::setLockFileState(const QString &serverRelativePath, const SyncFileItem::LockStatus lock)
 {
     const auto job = new LockFileJob(accountState()->account(), &_journal, serverRelativePath, lock);
+    connect(job, &LockFileJob::finishedWithError, [lock, serverRelativePath](const int httpErrorCode, const QString &errorString, const QString &lockOwnerName) {
+        auto errorMessage = QString{};
+        const auto filePath = serverRelativePath.mid(1);
+
+        if (httpErrorCode == LockFileJob::LOCKED_HTTP_ERROR_CODE) {
+            errorMessage = tr("File %1 is already locked by %2.").arg(filePath, lockOwnerName);
+        } else if (lock == SyncFileItem::LockStatus::LockedItem) {
+             errorMessage = tr("Lock operation on %1 failed with error %2").arg(filePath, errorString);
+        } else if (lock == SyncFileItem::LockStatus::UnlockedItem) {
+             errorMessage = tr("Unlock operation on %1 failed with error %2").arg(filePath, errorString);
+        }
+        emit Systray::instance()->showErrorMessageDialog(errorMessage);
+    });
     job->start();
 }
 
diff --git a/src/gui/systray.h b/src/gui/systray.h
index 0b4aabc3ec79b..e3e974e6d4844 100644
--- a/src/gui/systray.h
+++ b/src/gui/systray.h
@@ -93,6 +93,7 @@ class Systray
     void openShareDialog(const QString &sharePath, const QString &localPath);
     void showFileActivityDialog(const QString &objectName, const int objectId);
     void sendChatMessage(const QString &token, const QString &message, const QString &replyTo);
+    void showErrorMessageDialog(const QString &error);
 
 public slots:
     void slotNewUserSelected();
diff --git a/src/gui/tray/Window.qml b/src/gui/tray/Window.qml
index c1c56039cf794..cfb6aaacd40c4 100644
--- a/src/gui/tray/Window.qml
+++ b/src/gui/tray/Window.qml
@@ -5,6 +5,7 @@ import QtQuick.Window 2.3
 import QtQuick.Controls 2.3
 import QtQuick.Layouts 1.2
 import QtGraphicalEffects 1.0
+import Qt.labs.platform 1.1 as NativeDialogs
 import "../"
 
 // Custom qml modules are in /theme (and included by resources.qrc)
@@ -62,6 +63,19 @@ Window {
         }
     }
 
+    Component {
+        id: errorMessageDialog
+
+        NativeDialogs.MessageDialog {
+            id: dialog
+
+            title: Systray.windowTitle
+
+            onAccepted: destroy()
+            onRejected: destroy()
+        }
+    }
+
     Connections {
         target: Systray
         function onShowWindow() {
@@ -84,6 +98,12 @@ Window {
         function onShowFileActivityDialog(objectName, objectId) {
             openFileActivityDialog(objectName, objectId)
         }
+
+        function onShowErrorMessageDialog(error) {
+            var newErrorDialog = errorMessageDialog.createObject(trayWindow)
+            newErrorDialog.text = error
+            newErrorDialog.open()
+        }
     }
 
     OpacityMask {