diff -r 7e75777e4a51 -r f35f6791595f mercurial/commands.py
--- a/mercurial/commands.py	Sun Aug 05 00:53:55 2018 -0700
+++ b/mercurial/commands.py	Sat Aug 04 12:43:41 2018 +0530
@@ -4546,10 +4546,15 @@
     if not (all or pats or show or mark or unmark):
         raise error.Abort(_('no files or directories specified'),
                          hint=('use --all to re-merge all unresolved files'))
+
     if mark and confirm and not pats:
         if ui.promptchoice(_(b'mark all unresolved files as resolved (yn)?'
                              b'$$ &Yes $$ &No')):
             raise error.Abort(_('user quit'))
+    if unmark and confirm and not pats:
+        if ui.promptchoice(_(b'mark all resolved files as unresolved (yn)?'
+                             b'$$ &Yes $$ &No')):
+            raise error.Abort(_('user quit'))
 
     if show:
         ui.pager('resolve')