Problem with integers in an array and print

I'm using Twine 2.0.11 and SugarCube 2.7.2

In the StoryInit passage I have the line

<<set $Strength to [1,0]>>

The first entry in the array is supposed to be the strength score, the second one the current training level for increasing it.

In the character sheet I'm using to keep track of variables while working I'm using

Strength <<print $Strength[0]>>, Training <<print $Strength[1]>>

to display the current values whenever I visit that passage.

Sadly, the second entry doesn't seem to exist. In fact, when I look at it in the debug view, the entire <<print...>> seems to be missing without any error messages.

I've just started to use arrays and widgets instead of ... less elegant solutions, but this is an error I can't seem to figure out.