diff --git a/lib/matplotlib/rcsetup.py b/lib/matplotlib/rcsetup.py
index fd89613e4abf..90661785268e 100644
--- a/lib/matplotlib/rcsetup.py
+++ b/lib/matplotlib/rcsetup.py
@@ -294,8 +294,8 @@ def validate_maskedarray(v):
 
 
 class validate_nseq_float(object):
-    def __init__(self, n=None):
-        self.n = n
+    def __init__(self, n=None, allow_none=False):
+        self.n, self.allow_none = n, allow_none
 
     def __call__(self, s):
         """return a seq of n floats or raise"""
@@ -309,7 +309,11 @@ def __call__(self, s):
             raise ValueError(err_msg.format(n=self.n, num=len(s), s=s))
 
         try:
-            return [float(val) for val in s]
+            return [float(val)
+                    if self.allow_none and val is not None
+                    or not self.allow_none
+                    else val
+                    for val in s]
         except ValueError:
             raise ValueError('Could not convert all entries to floats')
 
@@ -697,7 +701,7 @@ def validate_hatch(s):
         raise ValueError("Unknown hatch symbol(s): %s" % list(unknown))
     return s
 validate_hatchlist = _listify_validator(validate_hatch)
-validate_dashlist = _listify_validator(validate_nseq_float())
+validate_dashlist = _listify_validator(validate_nseq_float(allow_none=True))
 
 _prop_validators = {
         'color': _listify_validator(validate_color_for_prop_cycle,
@@ -929,7 +933,6 @@ def _validate_linestyle(ls):
     raise ValueError("linestyle must be a string or " +
                      "an even-length sequence of floats.")
 
-
 # a map from key -> value, converter
 defaultParams = {
     'backend':           ['Agg', validate_backend],  # agg is certainly
@@ -964,7 +967,8 @@ def _validate_linestyle(ls):
     'lines.dash_capstyle':   ['butt', validate_capstyle],
     'lines.solid_capstyle':  ['projecting', validate_capstyle],
     'lines.dashed_pattern':  [[3.7, 1.6], validate_nseq_float()],
-    'lines.dashdot_pattern': [[6.4, 1.6, 1, 1.6], validate_nseq_float()],
+    'lines.dashdot_pattern': [[6.4, 1.6, 1, 1.6],
+                              validate_nseq_float()],
     'lines.dotted_pattern':  [[1, 1.65], validate_nseq_float()],
     'lines.scale_dashes':  [True, validate_bool],