Change choropleth hover format

Hi all,

I would like to change the format of hover data, namely decrease the floating point precision. As described in choropleth doc, I try to pass a dict with my format string as argument to hover_data :

px.choropleth(data_frame= pop_perstate
              ,color = 2000 
              , locations = "State"          
              ,locationmode = "USA-states"
              ,scope = "usa"
              , hover_data = {"State" : True, 2000 :  ':.3f'}

But this does not work and I got the following error :

RuntimeError: dictionary changed size during iteration

What is wrong with the call ?
Many thanks;