--- a/eric6/QScintilla/Editor.py Mon Apr 20 19:49:15 2020 +0200 +++ b/eric6/QScintilla/Editor.py Tue Apr 21 19:44:19 2020 +0200 @@ -7144,7 +7144,12 @@ @param evt reference to the event (QEvent) @return flag indiating that the event was handled (boolean) """ - self.__markerMap.calculateGeometry() + try: + self.__markerMap.calculateGeometry() + except AttributeError: + # ignore this - there seems to be a runtime issue when the editor + # is created + pass return super(Editor, self).viewportEvent(evt) def __updateReadOnly(self, bForce=True):