diff --git a/hgext/fsmonitor/__init__.py b/hgext/fsmonitor/__init__.py
--- a/hgext/fsmonitor/__init__.py
+++ b/hgext/fsmonitor/__init__.py
@@ -236,8 +236,8 @@
 
     """
     sha1 = hashlib.sha1()
-    sha1.update(repr(ignore))
-    return sha1.hexdigest()
+    sha1.update(pycompat.byterepr(ignore))
+    return pycompat.sysbytes(sha1.hexdigest())
 
 
 _watchmanencoding = pywatchman.encoding.get_local_encoding()