diff --git a/metcalcpy/sum_stat.py b/metcalcpy/sum_stat.py
index 7a1db3bd..65c02de1 100644
--- a/metcalcpy/sum_stat.py
+++ b/metcalcpy/sum_stat.py
@@ -182,6 +182,7 @@ def aggregate_special_fields(self, axis='1'):
         Args:
             axis - y1 or y1 axis
         """
+        warnings.filterwarnings('error')
 
         # check if indy_vals have a field that need to be aggregated - the field with ';'
         has_agg_indy_field = any(any(GROUP_SEPARATOR in i for i in item) for item in self.params['indy_vals'])
@@ -235,7 +236,7 @@ def aggregate_special_fields(self, axis='1'):
                                                             point_data,
                                                             self.params['line_type'])
 
-                    aggregated_values = aggregated_values.append(point_data)
+                    aggregated_values = pd.concat([aggregated_values, point_data])
             self.input_data = aggregated_values
             self.input_data.reset_index(inplace=True, drop=True)