diff -r 242ad45b60b3 -r a71578ec6257 mercurial/commands.py
--- a/mercurial/commands.py	Sun Oct 27 12:30:59 2019 +0900
+++ b/mercurial/commands.py	Sun Oct 27 12:36:52 2019 +0900
@@ -2269,6 +2269,10 @@
             fm.write(b'name value', b'%s=%s\n', entryname, value)
         if formatter.isprintable(defaultvalue):
             fm.data(defaultvalue=defaultvalue)
+        elif isinstance(defaultvalue, list) and all(
+            formatter.isprintable(e) for e in defaultvalue
+        ):
+            fm.data(defaultvalue=fm.formatlist(defaultvalue, name=b'value'))
         # TODO: no idea how to process unsupported defaultvalue types
         matched = True
     fm.end()