diff --git a/doc/gendoc.py b/doc/gendoc.py
--- a/doc/gendoc.py
+++ b/doc/gendoc.py
@@ -85,7 +85,12 @@
         if b'\n' in desc:
             # only remove line breaks and indentation
             desc = b' '.join(l.lstrip() for l in desc.split(b'\n'))
-        desc += default and _(b" (default: %s)") % bytes(default) or b""
+        if default:
+            defaulttmpl = _(b" (default: %s)")
+            if defaulttmpl:
+                if not isinstance(default, bytes):
+                    default = repr(default).encode('latin1')
+                desc += defaulttmpl % default
         yield (b", ".join(allopts), desc)