diff -r 3a57eafd8401 Lib/test/test_zlib.py
--- a/Lib/test/test_zlib.py	Tue May 24 09:15:14 2016 +0300
+++ b/Lib/test/test_zlib.py	Wed Jun 01 22:59:05 2016 +0800
@@ -557,6 +557,15 @@
                 self.assertEqual(dco.unconsumed_tail, b'')
                 self.assertEqual(dco.unused_data, remainder)
 
+    # issue27164
+    def test_decompress_raw_with_dictionary(self):
+        zdict = b'abcdefghijklmnopqrstuvwxyz'
+        co = zlib.compressobj(wbits=-zlib.MAX_WBITS, zdict=zdict)
+        comp = co.compress(zdict) + co.flush()
+        dco = zlib.decompressobj(wbits=-zlib.MAX_WBITS, zdict=zdict)
+        uncomp = dco.decompress(comp) + dco.flush()
+        self.assertEqual(zdict, uncomp)
+
     def test_flush_with_freed_input(self):
         # Issue #16411: decompressor accesses input to last decompress() call
         # in flush(), even if this object has been freed in the meanwhile.
diff -r 3a57eafd8401 Modules/zlibmodule.c
--- a/Modules/zlibmodule.c	Tue May 24 09:15:14 2016 +0300
+++ b/Modules/zlibmodule.c	Wed Jun 01 22:59:05 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);