diff --git a/mercurial/commands.py b/mercurial/commands.py
--- a/mercurial/commands.py
+++ b/mercurial/commands.py
@@ -2759,7 +2759,7 @@ def help_(ui, name=None, **opts):
     Returns 0 if successful.
     """
 
-    keep = opts.get('system') or []
+    keep = opts.get(r'system') or []
     if len(keep) == 0:
         if pycompat.sysplatform.startswith('win'):
             keep.append('windows')
diff --git a/mercurial/help.py b/mercurial/help.py
--- a/mercurial/help.py
+++ b/mercurial/help.py
@@ -23,6 +23,7 @@ from . import (
     filemerge,
     fileset,
     minirst,
+    pycompat,
     revset,
     templatefilters,
     templatekw,
@@ -304,6 +305,7 @@ def help_(ui, name, unknowncmd=False, fu
     '''
 
     from . import commands # avoid cycle
+    opts = pycompat.byteskwargs(opts)
 
     def helpcmd(name, subtopic=None):
         try: