diff -r c5729c10ce65 Doc/library/zlib.rst
--- a/Doc/library/zlib.rst	Mon May 02 13:45:20 2016 +0300
+++ b/Doc/library/zlib.rst	Mon May 02 15:12:41 2016 +0300
@@ -57,7 +57,7 @@ The available exception and functions in
    Raises the :exc:`error` exception if any error occurs.
 
    .. versionchanged:: 3.6
-      Keyword arguments are now supported.
+      *level* is now supported as keyword arguments.
 
 
 .. function:: compressobj(level=-1, method=DEFLATED, wbits=15, memLevel=8, strategy=Z_DEFAULT_STRATEGY[, zdict])
diff -r c5729c10ce65 Lib/test/test_zlib.py
--- a/Lib/test/test_zlib.py	Mon May 02 13:45:20 2016 +0300
+++ b/Lib/test/test_zlib.py	Mon May 02 15:12:41 2016 +0300
@@ -163,8 +163,10 @@ class CompressTestCase(BaseCompressTestC
         self.assertEqual(zlib.decompress(x), HAMLET_SCENE)
 
     def test_keywords(self):
-        x = zlib.compress(data=HAMLET_SCENE, level=3)
+        x = zlib.compress(HAMLET_SCENE, level=3)
         self.assertEqual(zlib.decompress(x), HAMLET_SCENE)
+        with self.assertRaises(TypeError):
+            zlib.compress(data=HAMLET_SCENE, level=3)
 
     def test_speech128(self):
         # compress more data
diff -r c5729c10ce65 Modules/clinic/zlibmodule.c.h
--- a/Modules/clinic/zlibmodule.c.h	Mon May 02 13:45:20 2016 +0300
+++ b/Modules/clinic/zlibmodule.c.h	Mon May 02 15:12:41 2016 +0300
@@ -3,7 +3,7 @@ preserve
 [clinic start generated code]*/
 
 PyDoc_STRVAR(zlib_compress__doc__,
-"compress($module, /, data, level=Z_DEFAULT_COMPRESSION)\n"
+"compress($module, data, /, level=Z_DEFAULT_COMPRESSION)\n"
 "--\n"
 "\n"
 "Returns a bytes object containing compressed data.\n"
@@ -23,7 +23,7 @@ static PyObject *
 zlib_compress(PyModuleDef *module, PyObject *args, PyObject *kwargs)
 {
     PyObject *return_value = NULL;
-    static char *_keywords[] = {"data", "level", NULL};
+    static char *_keywords[] = {"", "level", NULL};
     Py_buffer data = {NULL, NULL};
     int level = Z_DEFAULT_COMPRESSION;
 
@@ -440,4 +440,4 @@ exit:
 #ifndef ZLIB_COMPRESS_COPY_METHODDEF
     #define ZLIB_COMPRESS_COPY_METHODDEF
 #endif /* !defined(ZLIB_COMPRESS_COPY_METHODDEF) */
-/*[clinic end generated code: output=e6f3b79e051ecc35 input=a9049054013a1b77]*/
+/*[clinic end generated code: output=6d7aefbce8cb56e8 input=a9049054013a1b77]*/
diff -r c5729c10ce65 Modules/zlibmodule.c
--- a/Modules/zlibmodule.c	Mon May 02 13:45:20 2016 +0300
+++ b/Modules/zlibmodule.c	Mon May 02 15:12:41 2016 +0300
@@ -139,6 +139,7 @@ zlib.compress
 
     data: Py_buffer
         Binary data to be compressed.
+    /
     level: int(c_default="Z_DEFAULT_COMPRESSION") = Z_DEFAULT_COMPRESSION
         Compression level, in 0-9 or -1.
 
@@ -147,7 +148,7 @@ Returns a bytes object containing compre
 
 static PyObject *
 zlib_compress_impl(PyModuleDef *module, Py_buffer *data, int level)
-/*[clinic end generated code: output=1b97589132b203b4 input=abed30f4fa14e213]*/
+/*[clinic end generated code: output=1b97589132b203b4 input=638d54b6315dbed3]*/
 {
     PyObject *ReturnVal = NULL;
     Byte *input, *output = NULL;