whatsnew

Author: jbrockmendel

doc/source/whatsnew/v1.3.0.rst

@@ -787,6 +787,7 @@ Groupby/resample/rolling
 - Bug in :meth:`Series.asfreq` and :meth:`DataFrame.asfreq` dropping rows when the index is not sorted (:issue:`39805`)
 - Bug in aggregation functions for :class:`DataFrame` not respecting ``numeric_only`` argument when ``level`` keyword was given (:issue:`40660`)
 - Bug in :class:`core.window.RollingGroupby` where ``as_index=False`` argument in ``groupby`` was ignored (:issue:`39433`)
+- Bug in :meth:`GroupBy.cummin` and :meth:`GroupBy.cummax` incorrectly rounding integer values near the ``int64`` implementations bounds (:issue:`40767`)
 
 Reshaping
 ^^^^^^^^^