s = """
    A GUI neutral radio button.

    For the buttons to remain responsive
    you must keep a reference to this object.

    The following attributes are exposed:

     *ax*
        The :class:`matplotlib.axes.Axes` instance the buttons are in

     *activecolor*
        The color of the button when clicked

     *labels*
        A list of :class:`matplotlib.text.Text` instances

     *circles*
        A list of :class:`matplotlib.patches.Circle` instances

     *value_selected*
        A string listing the current value selected

    Connect to the RadioButtons with the :meth:`on_clicked` method
    """

from inspect import cleandoc
from matplotlib.cbook import dedent

%timeit cleandoc(s)
27.3 µs ± 859 ns per loop (mean ± std. dev. of 7 runs, 10000 loops each)

%timeit dedent(s)
10.4 µs ± 172 ns per loop (mean ± std. dev. of 7 runs, 100000 loops each)

diff --git c/lib/matplotlib/docstring.py w/lib/matplotlib/docstring.py
index 79ea63a96..88b7a022b 100644
--- c/lib/matplotlib/docstring.py
+++ w/lib/matplotlib/docstring.py
@@ -112,7 +112,7 @@ interpd = Substitution()
 
 def dedent_interpd(func):
     """Dedent *func*'s docstring, then interpolate it with ``interpd``."""
-    func.__doc__ = inspect.getdoc(func.__doc__)
+    func.__doc__ = inspect.getdoc(func)
     return interpd(func)