diff --git a/setup.py b/setup.py
--- a/setup.py
+++ b/setup.py
@@ -1,4 +1,4 @@
-import sys
+import hashlib
 
 from setuptools import setup
 
@@ -16,8 +16,11 @@
 
 
 extra_requirements = []
-if sys.version_info < (3, 5):
-    extra_requirements = ['pyblake2']
+
+
+pyblake2_hashes = {'blake2s256', 'blake2b512'}
+if pyblake2_hashes - set(hashlib.algorithms_available):
+    extra_requirements.append('pyblake2')
 
 setup(
     name='swh.model',
diff --git a/swh/model/hashutil.py b/swh/model/hashutil.py
--- a/swh/model/hashutil.py
+++ b/swh/model/hashutil.py
@@ -28,7 +28,6 @@
 import functools
 import hashlib
 import os
-import sys
 
 from io import BytesIO
 
@@ -42,14 +41,15 @@
 # FWIW coreutils' sha1sum uses 32768
 HASH_BLOCK_SIZE = 32768
 
-# Prior to python3.4, only blake2 is available through pyblake2 module
-# From 3.5 onwards, it's been integrated in python
-if sys.version_info.major == 3 and sys.version_info.minor <= 4:
-    import pyblake2
-    # register those hash algorithms in hashlib
-    __cache = hashlib.__builtin_constructor_cache
-    __cache['blake2s256'] = pyblake2.blake2s
-    __cache['blake2b512'] = pyblake2.blake2b
+# Load blake2 hashes from pyblake2 if they are not available in the builtin
+# hashlib
+__pyblake2_hashes = {'blake2s256': 'blake2s',
+                     'blake2b512': 'blake2b'}
+__cache = hashlib.__builtin_constructor_cache
+for __hash, __pyblake2_fn in __pyblake2_hashes.items():
+    if __hash not in hashlib.algorithms_available:
+        import pyblake2
+        __cache[__hash] = getattr(pyblake2, __pyblake2_fn)
 
 
 def _new_git_hash(base_algo, git_type, length):