diff -r 136adbcefa5f -r 4ba7bb701def Doc/library/zlib.rst
--- a/Doc/library/zlib.rst	Sun Jan 03 18:00:31 2016 -0800
+++ b/Doc/library/zlib.rst	Mon Feb 01 18:56:11 2016 +0200
@@ -46,14 +46,19 @@
       platforms, use ``adler32(data) & 0xffffffff``.
 
 
-.. function:: compress(data[, level])
+.. function:: compress(data, level=-1)
 
    Compresses the bytes in *data*, returning a bytes object containing compressed data.
-   *level* is an integer from ``0`` to ``9`` controlling the level of compression;
+   *level* is an integer from ``0`` to ``9`` or ``-1`` controlling the level of compression;
    ``1`` is fastest and produces the least compression, ``9`` is slowest and
-   produces the most.  ``0`` is no compression.  The default value is ``6``.
+   produces the most.  ``0`` is no compression. The default value is ``-1`` 
+   (Z_DEFAULT_COMPRESSION). Z_DEFAULT_COMPRESSION represents a default
+   compromise between speed and compression (currently equivalent to level 6).
    Raises the :exc:`error` exception if any error occurs.
 
+   .. versionchanged:: 3.6
+      *level* is a keyword argument.
+
 
 .. function:: compressobj(level=-1, method=DEFLATED, wbits=15, memLevel=8, strategy=Z_DEFAULT_STRATEGY[, zdict])
 
diff -r 136adbcefa5f -r 4ba7bb701def Modules/clinic/zlibmodule.c.h
--- a/Modules/clinic/zlibmodule.c.h	Sun Jan 03 18:00:31 2016 -0800
+++ b/Modules/clinic/zlibmodule.c.h	Mon Feb 01 18:56:11 2016 +0200
@@ -3,38 +3,39 @@
 [clinic start generated code]*/
 
 PyDoc_STRVAR(zlib_compress__doc__,
-"compress($module, bytes, level=Z_DEFAULT_COMPRESSION, /)\n"
+"compress($module, /, data, level=Z_DEFAULT_COMPRESSION)\n"
 "--\n"
 "\n"
 "Returns a bytes object containing compressed data.\n"
 "\n"
-"  bytes\n"
+"  data\n"
 "    Binary data to be compressed.\n"
 "  level\n"
 "    Compression level, in 0-9.");
 
 #define ZLIB_COMPRESS_METHODDEF    \
-    {"compress", (PyCFunction)zlib_compress, METH_VARARGS, zlib_compress__doc__},
+    {"compress", (PyCFunction)zlib_compress, METH_VARARGS|METH_KEYWORDS, zlib_compress__doc__},
 
 static PyObject *
-zlib_compress_impl(PyModuleDef *module, Py_buffer *bytes, int level);
+zlib_compress_impl(PyModuleDef *module, Py_buffer *data, int level);
 
 static PyObject *
-zlib_compress(PyModuleDef *module, PyObject *args)
+zlib_compress(PyModuleDef *module, PyObject *args, PyObject *kwargs)
 {
     PyObject *return_value = NULL;
-    Py_buffer bytes = {NULL, NULL};
+    static char *_keywords[] = {"data", "level", NULL};
+    Py_buffer data = {NULL, NULL};
     int level = Z_DEFAULT_COMPRESSION;
 
-    if (!PyArg_ParseTuple(args, "y*|i:compress",
-        &bytes, &level))
+    if (!PyArg_ParseTupleAndKeywords(args, kwargs, "y*|i:compress", _keywords,
+        &data, &level))
         goto exit;
-    return_value = zlib_compress_impl(module, &bytes, level);
+    return_value = zlib_compress_impl(module, &data, level);
 
 exit:
-    /* Cleanup for bytes */
-    if (bytes.obj)
-       PyBuffer_Release(&bytes);
+    /* Cleanup for data */
+    if (data.obj)
+       PyBuffer_Release(&data);
 
     return return_value;
 }
@@ -438,4 +439,4 @@
 #ifndef ZLIB_COMPRESS_COPY_METHODDEF
     #define ZLIB_COMPRESS_COPY_METHODDEF
 #endif /* !defined(ZLIB_COMPRESS_COPY_METHODDEF) */
-/*[clinic end generated code: output=7734aec079550bc8 input=a9049054013a1b77]*/
+/*[clinic end generated code: output=3dce3942efa9497c input=a9049054013a1b77]*/
diff -r 136adbcefa5f -r 4ba7bb701def Modules/zlibmodule.c
--- a/Modules/zlibmodule.c	Sun Jan 03 18:00:31 2016 -0800
+++ b/Modules/zlibmodule.c	Mon Feb 01 18:56:11 2016 +0200
@@ -137,18 +137,17 @@
 /*[clinic input]
 zlib.compress
 
-    bytes: Py_buffer
+    data: Py_buffer
         Binary data to be compressed.
     level: int(c_default="Z_DEFAULT_COMPRESSION") = Z_DEFAULT_COMPRESSION
         Compression level, in 0-9.
-    /
 
 Returns a bytes object containing compressed data.
 [clinic start generated code]*/
 
 static PyObject *
-zlib_compress_impl(PyModuleDef *module, Py_buffer *bytes, int level)
-/*[clinic end generated code: output=5d7dd4588788efd3 input=be3abe9934bda4b3]*/
+zlib_compress_impl(PyModuleDef *module, Py_buffer *data, int level)
+/*[clinic end generated code: output=1b97589132b203b4 input=671c615a4b2267da]*/
 {
     PyObject *ReturnVal = NULL;
     Byte *input, *output = NULL;
@@ -156,13 +155,13 @@
     int err;
     z_stream zst;
 
-    if ((size_t)bytes->len > UINT_MAX) {
+    if ((size_t)data->len > UINT_MAX) {
         PyErr_SetString(PyExc_OverflowError,
                         "Size does not fit in an unsigned int");
         goto error;
     }
-    input = bytes->buf;
-    length = (unsigned int)bytes->len;
+    input = data->buf;
+    length = (unsigned int)data->len;
 
     zst.avail_out = length + length/1000 + 12 + 1;