diff --git a/plugins/3MFReader/WorkspaceDialog.py b/plugins/3MFReader/WorkspaceDialog.py
index 7c803486eb..5e5eaf985e 100644
--- a/plugins/3MFReader/WorkspaceDialog.py
+++ b/plugins/3MFReader/WorkspaceDialog.py
@@ -272,12 +272,26 @@ class WorkspaceDialog(QObject):
     def notifyClosed(self):
         self._result = {} # The result should be cleared before hide, because after it is released the main thread lock
         self._visible = False
-        self._lock.release()
+        try:
+            self._lock.release()
+        except:
+            pass
 
     def hide(self):
         self._visible = False
         self._view.hide()
-        self._lock.release()
+        try:
+            self._lock.release()
+        except:
+            pass
+
+    @pyqtSlot(bool)
+    def _onVisibilityChanged(self, visible):
+        if not visible:
+            try:
+                self._lock.release()
+            except:
+                pass
 
     @pyqtSlot()
     def onOkButtonClicked(self):
@@ -290,7 +304,6 @@ class WorkspaceDialog(QObject):
         self._view.hide()
         self.hide()
 
-
     ##  Block thread until the dialog is closed.
     def waitForClose(self):
         if self._visible:
diff --git a/plugins/3MFReader/WorkspaceDialog.qml b/plugins/3MFReader/WorkspaceDialog.qml
index e9ef14dfa5..a633491248 100644
--- a/plugins/3MFReader/WorkspaceDialog.qml
+++ b/plugins/3MFReader/WorkspaceDialog.qml
@@ -10,6 +10,7 @@ import UM 1.1 as UM
 
 UM.Dialog
 {
+    id: base
     title: catalog.i18nc("@title:window", "Open Project")
 
     minimumWidth: 500 * screenScaleFactor
@@ -30,6 +31,7 @@ UM.Dialog
             materialResolveComboBox.currentIndex = 0
         }
     }
+
     Item
     {
         anchors.fill: parent
@@ -377,7 +379,7 @@ UM.Dialog
             anchors.right: ok_button.left
             anchors.rightMargin: 2 * screenScaleFactor
         }
-         Button
+        Button
         {
             id: ok_button
             text: catalog.i18nc("@action:button","Open");
@@ -386,4 +388,10 @@ UM.Dialog
             anchors.right: parent.right
         }
     }
+
+    function reject() {
+        manager.onCancelButtonClicked();
+        base.visible = false;
+        base.rejected();
+    }
 }