diff --git a/Lib/cmp.py b/Lib/cmp.py
index 69e6e27..f21d3a2 100644
--- a/Lib/cmp.py
+++ b/Lib/cmp.py
@@ -12,14 +12,14 @@
 
 cache = {}
 
-def cmp(f1, f2): # Compare two files, use the cache if possible.
+def cmp(f1, f2, shallow=1): # Compare two files, use the cache if possible.
 	# Return 1 for identical files, 0 for different.
 	# Raise exceptions if either file could not be statted, read, etc.
 	s1, s2 = sig(os.stat(f1)), sig(os.stat(f2))
 	if s1[0] <> 8 or s2[0] <> 8:
 		# Either is a not a plain file -- always report as different
 		return 0
-	if s1 == s2:
+	if shallow and s1 == s2:
 		# type, size & mtime match -- report same
 		return 1
 	if s1[:2] <> s2[:2]: # Types or sizes differ, don't bother
@@ -52,8 +52,8 @@
 
 def do_cmp(f1, f2): # Compare two files, really
 	bufsize = 8*1024 # Could be tuned
-	fp1 = open(f1, 'r')
-	fp2 = open(f2, 'r')
+	fp1 = open(f1, 'rb')
+	fp2 = open(f2, 'rb')
 	while 1:
 		b1 = fp1.read(bufsize)
 		b2 = fp2.read(bufsize)