bug in ExpressionCombine

[Tesshub]

Following expression does not work :
"U_value_additioned": [
["ExpressionCombine", [
{
"Uw": "Uw__W/m²K__Ucalc__westwall",
"Ue": "Ue__W/m²K__Ucalc__eastwall",
"Ud": "Ud__W/m²K__Ucalc__door",
"Uf": "Uf__W/m²K__Ucalc__floor",
"Uc": "Uc__W/m²K__Ucalc__ceiling",
},
"Uw + Ue + Ud + Uf + Uc ",
'Utot_from_hfs__W/m²K__Ucalc__in',
]],],

As "Uc" (last variable) is the same beginning as "Ucalc", bloc1.

Get error:

Though for a long time it was due to special character "²" but no. Changed Uc to Ux, and it works just fine.