diff --git a/mercurial/utils/stringutil.py b/mercurial/utils/stringutil.py
--- a/mercurial/utils/stringutil.py
+++ b/mercurial/utils/stringutil.py
@@ -27,7 +27,8 @@
 # regex special chars pulled from https://bugs.python.org/issue29995
 # which was part of Python 3.7.
 _respecial = pycompat.bytestr(b'()[]{}?*+-|^$\\.&~# \t\n\r\v\f')
-_regexescapemap = {ord(i): (b'\\' + i).decode('latin1') for i in _respecial}
+_regexescapemapb = {i: (b'\\' + i) for i in _respecial}
+_regexescapemapu = {ord(i): (b'\\' + i).decode('latin1') for i in _respecial}
 
 def reescape(pat):
     """Drop-in replacement for re.escape."""
@@ -36,9 +37,13 @@
     # unicode.translate, not bytes.translate. Sigh.
     wantuni = True
     if isinstance(pat, bytes):
+        if len(pat) == 1:
+            # fast path for hgignore parsing, which calls this on one
+            # char at a time
+            return _regexescapemapb.get(pat, pat)
         wantuni = False
         pat = pat.decode('latin1')
-    pat = pat.translate(_regexescapemap)
+    pat = pat.translate(_regexescapemapu)
     if wantuni:
         return pat
     return pat.encode('latin1')