diff --git a/CAL/CalibrationCommon/lib/datacontainers/holography_observation.py b/CAL/CalibrationCommon/lib/datacontainers/holography_observation.py
index 0261e39466576e57b4bc1b6c46b63677c85b7957..af15f5114a3786142d67072f770bcbd38b464311 100644
--- a/CAL/CalibrationCommon/lib/datacontainers/holography_observation.py
+++ b/CAL/CalibrationCommon/lib/datacontainers/holography_observation.py
@@ -103,7 +103,7 @@ class HolographyObservation():
         for root, dirnames, filenames in os.walk(path):
             match = re.match(ms_dirs_path_pattern, root)
             if match:
-                sas_id = match.group('sas_id')
+                sas_id = int(match.group('sas_id'))
 
                 ms_indexed_per_beamlet_number = HolographyObservation. \
                     create_ms_dict_from_ms_name_list_and_path(dirnames, root)
@@ -111,11 +111,11 @@ class HolographyObservation():
 
                 start_mjd_in_seconds, end_mjd_in_seconds = HolographyObservation.\
                     __compute_time_range_from_ms_list(
-                    ms_indexed_per_beamlet_number.values())
+                    list(ms_indexed_per_beamlet_number.values()))
 
                 unique_frequencies = HolographyObservation. \
                     extract_unique_reference_frequencies_from_ms_list(
-                    ms_indexed_per_beamlet_number.values())
+                    list(ms_indexed_per_beamlet_number.values()))
 
                 if len(unique_frequencies) == 1:
                     frequency = unique_frequencies.pop()
@@ -124,7 +124,8 @@ class HolographyObservation():
                         'Multiple reference frequencies per observation are not supported')
 
                 unique_source_names = HolographyObservation.\
-                    extract_unique_source_names_from_ms_list(ms_indexed_per_beamlet_number.values())
+                    extract_unique_source_names_from_ms_list(
+                    list(ms_indexed_per_beamlet_number.values()))
 
                 if len(unique_source_names) == 1:
                     source_name = unique_source_names.pop()
@@ -133,7 +134,8 @@ class HolographyObservation():
                         'Multiple source target per observation are not supported')
 
                 unique_subband = HolographyObservation.\
-                    extract_unique_subband_from_ms_list(ms_indexed_per_beamlet_number.values())
+                    extract_unique_subband_from_ms_list(
+                    list(ms_indexed_per_beamlet_number.values()))
 
                 if len(unique_subband) == 1:
                     sub_band = unique_subband.pop()