Accessing Sugarcube story across Mac and Windows

Hi all,

Short version: Can I open up the same tws file on both Mac and Windows if I'm using Sugarcube?

Long version:

I'm using Sugarcube with Twine 1.4.2. I normally work on my Macbook but today I felt like working on my Twine game on my Windows desktop. I dropped the Twine into Dropbox, but when I open the tws file on Windows I'm getting this error message:

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An error occurred while opening your story.

Traceback (most recent call last):

File "app.py, line 103, in open
File "storyframe.pyo", line 32, in __init__
File "storyframe.pyo", line 1122, in setTarget
KeyError: "sugarcube-2.py"

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I'm pretty sure I installed Sugarcube correctly on Windows; I can see Sugarcube from the Story Formats list and it seems I can make a Sugarcube story just fine on my Windows machine. In fact, I made a brand new Sugarcube Twine on my Windows machine, then placed it in Dropbox. When I try to open the new Twine game on my Mac, I get a similar error message:

---

An error occurred while opening your story.

Traceback (most recent call last):

File "/Users/myname/Desktop/twine_1.4.2_osx/Twine.app/Contents/Resources/app.py", line 103, in open
File "storyframe.pyo", line 32, in __init__
File "storyframe.pyo", line 1114, in setTarget
KeyError: "sugarcube-2"

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So, do any Sugarcube wizards know what's causing this error and how I can fix it?

Thanks for you help!