diff -r a42369e04aee -r a339027902c4 mercurial/commands.py
--- a/mercurial/commands.py	Fri Jul 07 23:40:00 2017 +0900
+++ b/mercurial/commands.py	Fri Jul 07 23:13:04 2017 +0900
@@ -4773,7 +4773,7 @@
         s = ' '.join(e.recordtypes)
         ui.warn(
             _('warning: merge state has unsupported record types: %s\n') % s)
-        unresolved = 0
+        unresolved = []
     else:
         unresolved = list(ms.unresolved())