diff --git a/mercurial/utils/stringutil.py b/mercurial/utils/stringutil.py
--- a/mercurial/utils/stringutil.py
+++ b/mercurial/utils/stringutil.py
@@ -46,6 +46,8 @@
         return '%d' % o
     elif isinstance(o, float):
         return '%f' % o
+    elif isinstance(o, tuple):
+        return '(%s)' % (b', '.join(pprint(a, bprefix=bprefix) for a in o))
     elif o is None:
         return b'None'
     else: