diff --git a/mhctools/__init__.py b/mhctools/__init__.py
index 129aa71..f541f64 100644
--- a/mhctools/__init__.py
+++ b/mhctools/__init__.py
@@ -23,7 +23,7 @@
 from .random_predictor import RandomBindingPredictor
 from .unsupported_allele import UnsupportedAllele
 
-__version__ = "1.8.2"
+__version__ = "1.9.0"
 
 __all__ = [
     "BindingPrediction",
diff --git a/mhctools/base_predictor.py b/mhctools/base_predictor.py
index 0e53b5a..aae8adc 100644
--- a/mhctools/base_predictor.py
+++ b/mhctools/base_predictor.py
@@ -242,7 +242,7 @@ def _check_hla_alleles(
         HLA alleles, return a set of alleles that we will pass into
         the MHC binding predictor.
         """
-        require_iterable_of(alleles, string_types, "HLA alleles")
+        require_iterable_of(alleles, str, "HLA alleles")
 
         # Don't run the MHC predictor twice for homozygous alleles,
         # only run it for unique alleles
diff --git a/mhctools/iedb.py b/mhctools/iedb.py
index 7a4f2b1..5762758 100644
--- a/mhctools/iedb.py
+++ b/mhctools/iedb.py
@@ -153,7 +153,7 @@ def __init__(
         # for not raising, since sometimes we want to be more permissive with IEDB predictors
         self.raise_on_error = raise_on_error
 
-        if not isinstance(url, string_types):
+        if not isinstance(url, str):
             raise TypeError("Expected URL to be string, not %s : %s" % (
                 url, type(url)))
         self.url = url
diff --git a/tests/test_netmhc_pan.py b/tests/test_netmhc_pan.py
index 78128bc..fd5d832 100644
--- a/tests/test_netmhc_pan.py
+++ b/tests/test_netmhc_pan.py
@@ -2,11 +2,7 @@
 
 from mhctools import NetMHCpan
 
-# Defining FileNotFoundError for Python 2.x
-try:
-    FileNotFoundError
-except NameError:
-    FileNotFoundError = IOError
+
 
 
 DEFAULT_ALLELE = 'HLA-A*02:01'