The return value of ra.to_string(sep='hms') is incorrect

Astropy Development
1 
from astropy.coordinates import SkyCoord
c = SkyCoord('15h34m57.1s +23d30m11s',frame='icrs',equinox='J2000')
print(c.ra.to_string(sep='hms'))

The output result is like this, which is obviously incorrect.

233h44m16.5s

Is this a bug or am I using it incorrectly?