diff --git a/tbparse/summary_reader.py b/tbparse/summary_reader.py
index 60e0da7..25b399a 100644
--- a/tbparse/summary_reader.py
+++ b/tbparse/summary_reader.py
@@ -849,7 +849,7 @@ def _get_default_cols(self, tag_to_events: Dict[str, ScalarEvent],
         length = 0
         for events in tag_to_events.values():
             length += len(events)
-        cols: Dict[str, Any] = defaultdict(lambda: [np.NaN] * length)
+        cols: Dict[str, Any] = defaultdict(lambda: [np.nan] * length)
         if 'dir_name' in self._extra_columns:
             cols['dir_name'] = [''] * length
         if 'file_name' in self._extra_columns: