diff -r a14012352f65 Lib/gzip.py
--- a/Lib/gzip.py	Mon Apr 28 13:08:28 2014 +0200
+++ b/Lib/gzip.py	Mon Apr 28 15:05:34 2014 +0200
@@ -134,7 +134,8 @@
     max_read_chunk = 10 * 1024 * 1024   # 10Mb
 
     def __init__(self, filename=None, mode=None,
-                 compresslevel=9, fileobj=None, mtime=None):
+                 compresslevel=9, fileobj=None, mtime=None,
+                 buffer_size=io.DEFAULT_BUFFER_SIZE):
         """Constructor for the GzipFile class.
 
         At least one of fileobj and filename must be given a
@@ -171,6 +172,8 @@
         return value of time.time() and of the st_mtime member of the
         object returned by os.stat().
 
+        If the buffer_size is omitted it defaults to DEFAULT_BUFFER_SIZE.
+
         """
 
         if mode and ('t' in mode or 'U' in mode):
@@ -215,6 +218,7 @@
         self.fileobj = fileobj
         self.offset = 0
         self.mtime = mtime
+        self.buffer_size = buffer_size
 
         if self.mode == WRITE:
             self._write_gzip_header()
@@ -355,7 +359,7 @@
         if self.extrasize <= 0 and self.fileobj is None:
             return b''
 
-        readsize = 1024
+        readsize = self.buffer_size
         if size < 0:        # get the whole thing
             while self._read(readsize):
                 readsize = min(self.max_read_chunk, readsize * 2)
@@ -410,8 +414,7 @@
             if self.fileobj is None:
                 return b''
             # Ensure that we don't return b"" if we haven't reached EOF.
-            # 1024 is the same buffering heuristic used in read()
-            while self.extrasize == 0 and self._read(max(n, 1024)):
+            while self.extrasize == 0 and self._read(max(n, self.buffer_size)):
                 pass
         offset = self.offset - self.extrastart
         remaining = self.extrasize
@@ -422,7 +425,7 @@
         self.extrasize = len(buf) + self.extrasize
         self.offset -= len(buf)
 
-    def _read(self, size=1024):
+    def _read(self, size=io.DEFAULT_BUFFER_SIZE):
         if self.fileobj is None:
             return False
 
@@ -560,18 +563,18 @@
             if offset < self.offset:
                 raise OSError('Negative seek in write mode')
             count = offset - self.offset
-            chunk = bytes(1024)
-            for i in range(count // 1024):
+            chunk = bytes(self.buffer_size)
+            for i in range(count // self.buffer_size):
                 self.write(chunk)
-            self.write(bytes(count % 1024))
+            self.write(bytes(count % self.buffer_size))
         elif self.mode == READ:
             if offset < self.offset:
                 # for negative seek, rewind and do positive seek
                 self.rewind()
             count = offset - self.offset
-            for i in range(count // 1024):
-                self.read(1024)
-            self.read(count % 1024)
+            for i in range(count // self.buffer_size):
+                self.read(self.buffer_size)
+            self.read(count % self.buffer_size)
 
         return self.offset
 
@@ -661,7 +664,7 @@
                 f = builtins.open(arg, "rb")
                 g = open(arg + ".gz", "wb")
         while True:
-            chunk = f.read(1024)
+            chunk = f.read(io.DEFAULT_BUFFER_SIZE)
             if not chunk:
                 break
             g.write(chunk)