Thonny - Problem showing shellview

Traceback (most recent call last):
  File "/home/blackhole/apps/thonny/lib/python3.7/site-packages/thonny/workbench.py", line 1470, in _show_views
    self.show_view(view_id, False)
  File "/home/blackhole/apps/thonny/lib/python3.7/site-packages/thonny/workbench.py", line 1647, in show_view
    view = self.get_view(view_id)
  File "/home/blackhole/apps/thonny/lib/python3.7/site-packages/thonny/workbench.py", line 1553, in get_view
    view = class_(self)  # View's master is workbench to allow making it maximized
  File "/home/blackhole/apps/thonny/lib/python3.7/site-packages/thonny/shell.py", line 119, in __init__
    undo=True,
  File "/home/blackhole/apps/thonny/lib/python3.7/site-packages/thonny/shell.py", line 1494, in __init__
    super().__init__(master, view, cnf=cnf, **kw)
  File "/home/blackhole/apps/thonny/lib/python3.7/site-packages/thonny/shell.py", line 311, in __init__
    super().__init__(master, cnf, **kw)
  File "/home/blackhole/apps/thonny/lib/python3.7/site-packages/thonny/ui_utils.py", line 818, in __init__
    master=master, style=style, tag_current_line=tag_current_line, cnf=cnf, **kw
  File "/home/blackhole/apps/thonny/lib/python3.7/site-packages/thonny/codeview.py", line 36, in __init__
    super().__init__(master=master, cnf=cnf, **kw)
  File "/home/blackhole/apps/thonny/lib/python3.7/site-packages/thonny/tktextext.py", line 207, in __init__
    self._reload_theme_options()
  File "/home/blackhole/apps/thonny/lib/python3.7/site-packages/thonny/codeview.py", line 70, in _reload_theme_options
    self._reload_syntax_options(event)
  File "/home/blackhole/apps/thonny/lib/python3.7/site-packages/thonny/codeview.py", line 74, in _reload_syntax_options
    self.set_syntax_options(_syntax_options)
  File "/home/blackhole/apps/thonny/lib/python3.7/site-packages/thonny/shell.py", line 1478, in set_syntax_options
    self.update_margin_color()
  File "/home/blackhole/apps/thonny/lib/python3.7/site-packages/thonny/shell.py", line 1482, in update_margin_color
    self.tag_configure("io", lmargincolor=get_syntax_options_for_tag("TEXT")["background"])
KeyError: 'background'