diff --git a/ihm/__init__.py b/ihm/__init__.py
index c929a6d..468889e 100644
--- a/ihm/__init__.py
+++ b/ihm/__init__.py
@@ -10,6 +10,7 @@
 """
 
 import itertools
+import numbers
 import re
 import sys
 # Handle different naming of urllib in Python 2/3
@@ -1600,12 +1601,12 @@ def __init__(self, entity, details=None, auth_seq_id_map=0, id=None,
         self.num_map = None
 
     def _get_auth_seq_id_ins_code(self, seq_id):
-        if isinstance(self.auth_seq_id_map, int):
+        if isinstance(self.auth_seq_id_map, numbers.Integral):
             return seq_id + self.auth_seq_id_map, None
         else:
             try:
                 ret = self.auth_seq_id_map[seq_id]
-                if isinstance(ret, (int, str)):
+                if isinstance(ret, (numbers.Integral, str)):
                     return ret, None
                 else:
                     return ret
diff --git a/ihm/dumper.py b/ihm/dumper.py
index d3b807b..18ded69 100644
--- a/ihm/dumper.py
+++ b/ihm/dumper.py
@@ -2,6 +2,7 @@
 
 import re
 import os
+import numbers
 import collections
 import operator
 import itertools
@@ -1465,10 +1466,10 @@ def _dump_template(self, template, sm, lp, ordinal):
             denom = int(denom)
         # Add offset only if seq_id_range isn't . or ?
         seq_id_begin = template.seq_id_range[0]
-        if isinstance(template.seq_id_range[0], int):
+        if isinstance(template.seq_id_range[0], numbers.Integral):
             seq_id_begin += off
         seq_id_end = template.seq_id_range[1]
-        if isinstance(template.seq_id_range[1], int):
+        if isinstance(template.seq_id_range[1], numbers.Integral):
             seq_id_end += off
         lp.write(id=next(ordinal),
                  starting_model_id=sm._id,