diff --git a/mercurial/configitems.py b/mercurial/configitems.py
--- a/mercurial/configitems.py
+++ b/mercurial/configitems.py
@@ -587,52 +587,52 @@
     default=None,
     generic=True,
 )
-coreconfigitem('merge-tools', r'.*\.args$',
+coreconfigitem('merge-tools', br'.*\.args$',
     default="$local $base $other",
     generic=True,
     priority=-1,
 )
-coreconfigitem('merge-tools', r'.*\.binary$',
+coreconfigitem('merge-tools', br'.*\.binary$',
     default=False,
     generic=True,
     priority=-1,
 )
-coreconfigitem('merge-tools', r'.*\.check$',
+coreconfigitem('merge-tools', br'.*\.check$',
     default=list,
     generic=True,
     priority=-1,
 )
-coreconfigitem('merge-tools', r'.*\.checkchanged$',
+coreconfigitem('merge-tools', br'.*\.checkchanged$',
     default=False,
     generic=True,
     priority=-1,
 )
-coreconfigitem('merge-tools', r'.*\.executable$',
+coreconfigitem('merge-tools', br'.*\.executable$',
     default=dynamicdefault,
     generic=True,
     priority=-1,
 )
-coreconfigitem('merge-tools', r'.*\.fixeol$',
+coreconfigitem('merge-tools', br'.*\.fixeol$',
     default=False,
     generic=True,
     priority=-1,
 )
-coreconfigitem('merge-tools', r'.*\.gui$',
+coreconfigitem('merge-tools', br'.*\.gui$',
     default=False,
     generic=True,
     priority=-1,
 )
-coreconfigitem('merge-tools', r'.*\.priority$',
+coreconfigitem('merge-tools', br'.*\.priority$',
     default=0,
     generic=True,
     priority=-1,
 )
-coreconfigitem('merge-tools', r'.*\.premerge$',
+coreconfigitem('merge-tools', br'.*\.premerge$',
     default=dynamicdefault,
     generic=True,
     priority=-1,
 )
-coreconfigitem('merge-tools', r'.*\.symlink$',
+coreconfigitem('merge-tools', br'.*\.symlink$',
     default=False,
     generic=True,
     priority=-1,