diff --git a/Lib/trace.py b/Lib/trace.py
index ade55bd5519..7f412633cf8 100644
--- a/Lib/trace.py
+++ b/Lib/trace.py
@@ -204,13 +204,11 @@ def __init__(self, counts=None, calledfuncs=None, infile=None,
         if self.infile:
             # Try to merge existing counts file.
             try:
-                counts, calledfuncs = pickle.load(open(self.infile, 'r'))
+                counts, calledfuncs = pickle.load(open(self.infile, 'rb'))
                 self.update(self.__class__(counts, calledfuncs))
             except (IOError, EOFError, ValueError), err:
                 print >> sys.stderr, ("Skipping counts file %r: %s"
                                       % (self.infile, err))
-            except pickle.UnpicklingError:
-                self.update(self.__class__(marshal.load(open(self.infile))))
 
     def update(self, other):
         """Merge in the data from another CoverageResults"""
@@ -288,7 +286,7 @@ def write_results(self, show_missing=True, summary=False, coverdir=None):
             # try and store counts and module info into self.outfile
             try:
                 pickle.dump((self.counts, self.calledfuncs),
-                            open(self.outfile, 'w'), 1)
+                            open(self.outfile, 'wb'), 1)
             except IOError, err:
                 print >> sys.stderr, "Can't save counts files because %s" % err