diff --git a/mercurial/revlog.py b/mercurial/revlog.py
--- a/mercurial/revlog.py
+++ b/mercurial/revlog.py
@@ -2099,7 +2099,7 @@
         if alwayscache and rawtext is None:
             rawtext = deltacomputer._buildtext(revinfo, fh)
 
-        if type(rawtext) == str: # only accept immutable objects
+        if type(rawtext) == bytes: # only accept immutable objects
             self._cache = (node, curr, rawtext)
         self._chainbasecache[curr] = chainbase
         return node