diff -r 81f8375e60ce Lib/zipfile.py
--- a/Lib/zipfile.py	Fri Dec 20 18:22:38 2013 +0200
+++ b/Lib/zipfile.py	Sat Dec 21 23:22:26 2013 +0200
@@ -606,7 +606,11 @@
         """Returns buffered bytes without advancing the position."""
         if n > len(self._readbuffer) - self._offset:
             chunk = self.read(n)
-            self._offset -= len(chunk)
+            if len(chunk) > self._offset:
+                self._readbuffer = chunk + self._readbuffer[self._offset:]
+                self._offset = 0
+            else:
+                self._offset -= len(chunk)
 
         # Return up to 512 bytes to reduce allocation overhead for tight loops.
         return self._readbuffer[self._offset: self._offset + 512]