diff --git a/mercurial/sparse.py b/mercurial/sparse.py
--- a/mercurial/sparse.py
+++ b/mercurial/sparse.py
@@ -173,12 +173,13 @@
         tempsignature = '0'
 
     if signature is None or (includetemp and tempsignature is None):
-        signature = hashlib.sha1(repo.vfs.tryread('sparse')).hexdigest()
+        signature = pycompat.bytestr(
+            hashlib.sha1(repo.vfs.tryread('sparse')).hexdigest())
         cache['signature'] = signature
 
         if includetemp:
             raw = repo.vfs.tryread('tempsparse')
-            tempsignature = hashlib.sha1(raw).hexdigest()
+            tempsignature = pycompat.bytestr(hashlib.sha1(raw).hexdigest())
             cache['tempsignature'] = tempsignature
 
     return '%s %s' % (signature, tempsignature)