diff -r df5f6881cebd -r 7fa3408f83ef mercurial/revlog.py
--- a/mercurial/revlog.py	Sat May 26 11:31:51 2018 +0900
+++ b/mercurial/revlog.py	Sat May 26 11:33:02 2018 +0900
@@ -855,7 +855,7 @@
     def rawsize(self, rev):
         """return the length of the uncompressed text for a given revision"""
         l = self.index[rev][2]
-        if l is not None and l >= 0:
+        if l >= 0:
             return l
 
         t = self.revision(rev, raw=True)