diff --git a/invisible_cities/io/mcinfo_io.py b/invisible_cities/io/mcinfo_io.py
index 728d47fad1..db479c315b 100644
--- a/invisible_cities/io/mcinfo_io.py
+++ b/invisible_cities/io/mcinfo_io.py
@@ -13,6 +13,7 @@
 
 from typing import List
 from typing import Optional
+from typing import Tuple
 from typing import Union
 
 
@@ -154,9 +155,9 @@ def __call__(self, mctables: (tb.Table, tb.Table, tb.Table, tb.Table),
         self.generator_table.flush()
 
 
-def is_newformat_file(file_name : str) -> bool:
+def is_oldformat_file(file_name : str) -> bool:
     with tb.open_file(file_name) as h5in:
-        return hasattr(h5in.root, 'MC/sns_positions')
+        return hasattr(h5in.root, 'MC/extents')
 
 
 def load_mchits_df(file_name : str) -> pd.DataFrame:
@@ -165,11 +166,11 @@ def load_mchits_df(file_name : str) -> pd.DataFrame:
     file_name : str
                 The name of the file to be read
     """
-    if is_newformat_file(file_name):
-        return load_mchits_dfnew(file_name)
-    else:
+    if is_oldformat_file(file_name):
         ## Is this a pre-Feb 2020 file?
         return load_mchits_dfold(file_name)
+    else:
+        return load_mchits_dfnew(file_name)
 
 
 def load_mchits_dfold(file_name : str) -> pd.DataFrame:
@@ -232,10 +233,10 @@ def load_mcparticles_df(file_name: str) -> pd.DataFrame:
     file_name : str
                 The name of the file to be read
     """
-    if is_newformat_file(file_name):
-        return load_mcparticles_dfnew(file_name)
-    else:
+    if is_oldformat_file(file_name):
         return load_mcparticles_dfold(file_name)
+    else:
+        return load_mcparticles_dfnew(file_name)
 
 
 def load_mcparticles_dfold(file_name: str) -> pd.DataFrame:
@@ -307,10 +308,10 @@ def get_sensor_binning(file_name : str) -> pd.DataFrame:
     input file and extracts the binning used
     for both types of sensitive detector.
     """
-    if is_newformat_file(file_name):
-        return sensor_binning_new(file_name)
-    else:
+    if is_oldformat_file(file_name):
         return sensor_binning_old(file_name)
+    else:
+        return sensor_binning_new(file_name)
 
 
 def sensor_binning_old(file_name : str) -> pd.DataFrame:
@@ -372,13 +373,13 @@ def load_mcsensor_response_df(file_name : str                 ,
                Sensor name of the data to be returned
                Default: return for every sensor
     """
-    if is_newformat_file(file_name):
-        return read_mcsensors_dfnew(file_name, sns_name)
-    else:
+    if is_oldformat_file(file_name):
         assert(db_file), "Database name required for this file"
         assert( run_no), "Run number required for database access"
         return read_mcsensors_dfold(file_name, db_file ,
                                     run_no   , sns_name)
+    else:
+        return read_mcsensors_dfnew(file_name, sns_name)
 
 
 def read_mcsensors_dfnew(file_name : str,