--- a/tests/run-tests.py	Fri Mar 06 23:27:28 2020 +0100
+++ b/tests/run-tests.py	Mon Mar 09 01:11:59 2020 +0100
@@ -1770,7 +1770,7 @@
 
         if self._case:
             casestr = b'#'.join(self._case)
-            if isinstance(self._case, str):
+            if isinstance(casestr, str):
                 quoted = shellquote(casestr)
             else:
                 quoted = shellquote(casestr.decode('utf8')).encode('utf8')