diff --git a/pandas/core/groupby/generic.py b/pandas/core/groupby/generic.py
index 01784513704b4..e646bfceb998d 100644
--- a/pandas/core/groupby/generic.py
+++ b/pandas/core/groupby/generic.py
@@ -63,7 +63,7 @@ def _iterate_slices(self):
             yield val, slicer(val)
 
     def _cython_agg_general(self, how, alt=None, numeric_only=True,
-                            min_count=-1):
+                            min_count=-1, skipna=True):
         new_items, new_blocks = self._cython_agg_blocks(
             how, alt=alt, numeric_only=numeric_only, min_count=min_count)
         return self._wrap_agged_blocks(new_items, new_blocks)