Small fix

Author: wouterpeere

pygfunction/borefield.py

@@ -111,7 +111,7 @@ def __add__(self,
                 other_field: Union[Borehole, List[Borehole], Self]) -> Self:
         """Add two borefields together"""
         if isinstance(other_field, Borehole):
-            return Borefield.from_boreholes(self.to_boreholes() + other_field)
+            return Borefield.from_boreholes(self.to_boreholes() + [other_field])
         if isinstance(other_field, list):
             return Borefield.from_boreholes(self.to_boreholes() + other_field)
         return Borefield.from_boreholes(self.to_boreholes() + other_field.to_boreholes())