diff -r ed4eec682199 Modules/zlibmodule.c
--- a/Modules/zlibmodule.c	Wed May 25 11:26:07 2016 -0700
+++ b/Modules/zlibmodule.c	Wed Jun 01 18:59:02 2016 +0800
@@ -22,6 +22,10 @@
     #define LEAVE_ZLIB(obj)
 #endif
 
+#if defined(ZLIB_VERNUM) && ZLIB_VERNUM >= 0x1221
+#define AT_LEAST_ZLIB_1_2_2_1
+#endif
+
 /* The following parameters are copied from zutil.h, version 0.95 */
 #define DEFLATED   8
 #if MAX_MEM_LEVEL >= 8
@@ -511,6 +515,36 @@
     switch(err) {
     case (Z_OK):
         self->is_initialised = 1;
+        if (self->zdict != NULL && wbits < 0) {
+#ifdef AT_LEAST_ZLIB_1_2_2_1
+            Py_buffer zdict_buf;
+            if (PyObject_GetBuffer(self->zdict, &zdict_buf, PyBUF_SIMPLE) == -1) {
+                Py_DECREF(self);
+                return NULL;
+            }
+            if ((size_t)zdict_buf.len > UINT_MAX) {
+                PyErr_SetString(PyExc_OverflowError,
+                                "zdict length does not fit in an unsigned int");
+                PyBuffer_Release(&zdict_buf);
+                Py_DECREF(self);
+                return NULL;
+            }
+            err = inflateSetDictionary(&(self->zst),
+                                       zdict_buf.buf, (unsigned int)zdict_buf.len);
+            PyBuffer_Release(&zdict_buf);
+            if (err != Z_OK) {
+                zlib_error(self->zst, err, "while setting zdict");
+                Py_DECREF(self);
+                return NULL;
+            }
+#else
+            PyErr_Format(ZlibError,
+                         "zlib version %s does not allow raw inflate with dictionary",
+                         ZLIB_VERSION);
+            Py_DECREF(self);
+            return NULL;
+#endif
+        }
         return (PyObject*)self;
     case(Z_STREAM_ERROR):
         Py_DECREF(self);