diff --git a/hgext/convert/common.py b/hgext/convert/common.py
--- a/hgext/convert/common.py
+++ b/hgext/convert/common.py
@@ -18,6 +18,7 @@
     encoding,
     error,
     phases,
+    pycompat,
     util,
 )
 
@@ -322,6 +323,7 @@
         pass
 
     def _cmdline(self, cmd, *args, **kwargs):
+        kwargs = pycompat.byteskwargs(kwargs)
         cmdline = [self.command, cmd] + list(args)
         for k, v in kwargs.iteritems():
             if len(k) == 1:
diff --git a/hgext/convert/convcmd.py b/hgext/convert/convcmd.py
--- a/hgext/convert/convcmd.py
+++ b/hgext/convert/convcmd.py
@@ -567,6 +567,7 @@
         self.map.close()
 
 def convert(ui, src, dest=None, revmapfile=None, **opts):
+    opts = pycompat.byteskwargs(opts)
     global orig_encoding
     orig_encoding = encoding.encoding
     encoding.encoding = 'UTF-8'
diff --git a/hgext/convert/cvsps.py b/hgext/convert/cvsps.py
--- a/hgext/convert/cvsps.py
+++ b/hgext/convert/cvsps.py
@@ -855,6 +855,7 @@
     repository, and convert the log to changesets based on matching
     commit log entries and dates.
     '''
+    opts = pycompat.byteskwargs(opts)
     if opts["new_cache"]:
         cache = "write"
     elif opts["update_cache"]:
diff --git a/hgext/convert/monotone.py b/hgext/convert/monotone.py
--- a/hgext/convert/monotone.py
+++ b/hgext/convert/monotone.py
@@ -13,6 +13,7 @@
 from mercurial.i18n import _
 from mercurial import (
     error,
+    pycompat,
     util,
 )
 
@@ -89,6 +90,7 @@
 
     def mtnrunstdio(self, *args, **kwargs):
         # Prepare the command in automate stdio format
+        kwargs = pycompat.byteskwargs(kwargs)
         command = []
         for k, v in kwargs.iteritems():
             command.append("%s:%s" % (len(k), k))