diff --git a/hgext/children.py b/hgext/children.py
--- a/hgext/children.py
+++ b/hgext/children.py
@@ -19,6 +19,7 @@
 from mercurial.i18n import _
 from mercurial import (
     cmdutil,
+    pycompat,
     registrar,
 )
 
@@ -55,6 +56,7 @@
     See :hg:`help log` and :hg:`help revsets.children`.
 
     """
+    opts = pycompat.byteskwargs(opts)
     rev = opts.get('rev')
     if file_:
         fctx = repo.filectx(file_, changeid=rev)