diff --git a/tests/hghave.py b/tests/hghave.py
--- a/tests/hghave.py
+++ b/tests/hghave.py
@@ -987,4 +987,4 @@
     version_regex = b'black, version ([0-9a-b.]+)'
     version = matchoutput(blackcmd, version_regex)
     sv = distutils.version.StrictVersion
-    return version and sv(version.group(1)) >= sv('19.10b0')
+    return version and sv(version.group(1).decode()) >= sv('19.10b0')