# Labels aren't displayed for layers inside a group

I'm using a python script to create an empty group layer in the current map document, add some layers to this group and update their symbology from an existing .lyr file.

I also want to to turn on these layers' labels using layer.showLabels = True and it works fine for normal layers, but for some reason it doesn't work on layers inside a group layer. However, when I manually drag these layers outside of the group, the labels are suddenly displayed, and they are still displayed when I drag the layers back into the group.

Does anyone has an idea why does it happen and how can I programmatically display the labels even for layers inside a group?

Thanks.

Edit:

Here is the relevant part (of a simplified version) of my ode:

mxd = arcpy.mapping.MapDocument("Current")
df = arcpy.mapping.ListDataFrames(mxd)[0]
groupLyr = arcpy.mapping.Layer(r'C:\Path\to\Group.lyr') # this is an empty group lyr file