diff --git a/hgext/rebase.py b/hgext/rebase.py
--- a/hgext/rebase.py
+++ b/hgext/rebase.py
@@ -1026,8 +1026,7 @@
         raise error.Abort(_(b'cannot specify both --dry-run and --%s') % action)
     if confirm and action:
         raise error.Abort(_(b'cannot specify both --confirm and --%s') % action)
-    if dryrun and confirm:
-        raise error.Abort(_(b'cannot specify both --confirm and --dry-run'))
+    cmdutil.check_unique_argument(opts, b'confirm', b'dry-run')
 
     if action or repo.currenttransaction() is not None:
         # in-memory rebase is not compatible with resuming rebases.
diff --git a/mercurial/cmdutil.py b/mercurial/cmdutil.py
--- a/mercurial/cmdutil.py
+++ b/mercurial/cmdutil.py
@@ -267,7 +267,7 @@
     """
     previous = None
     for x in args:
-        if opts.get(x):
+        if opts.get(x.replace(b'-', b'_')):
             if previous:
                 raise error.Abort(
                     _(b'cannot specify both --%s and --%s') % (previous, x)