diff --git a/mercurial/transaction.py b/mercurial/transaction.py
--- a/mercurial/transaction.py
+++ b/mercurial/transaction.py
@@ -418,7 +418,7 @@
     def readjournal(self):
         self._file.seek(0)
         entries = []
-        for l in self._file:
+        for l in self._file.readlines():
             file, troffset = l.split(b'\0')
             entries.append((file, int(troffset)))
         return entries