diff --git a/setup/extensions.json b/setup/extensions.json
index a22f98df65..6e22528dd8 100644
--- a/setup/extensions.json
+++ b/setup/extensions.json
@@ -31,7 +31,8 @@
         "inc_dirs": "!zlib_inc_dirs",
         "lib_dirs": "!zlib_lib_dirs",
         "libraries": "z",
-        "windows_libraries": "zlib"
+        "windows_libraries": "zlib",
+        "needs_py2": true
     },
     {
         "name": "certgen",
diff --git a/src/calibre/srv/http_response.py b/src/calibre/srv/http_response.py
index ead9aa4d6f..4d51ea1e21 100644
--- a/src/calibre/srv/http_response.py
+++ b/src/calibre/srv/http_response.py
@@ -12,9 +12,8 @@ from io import BytesIO, DEFAULT_BUFFER_SIZE
 from itertools import chain, repeat, izip_longest
 from operator import itemgetter
 from functools import wraps
-from polyglot.builtins import map
 
-from polyglot.builtins import reraise
+from polyglot.builtins import reraise, map, is_py3
 
 from calibre import guess_type, force_unicode
 from calibre.constants import __version__, plugins
@@ -31,10 +30,13 @@ from calibre.utils.monotonic import monotonic
 Range = namedtuple('Range', 'start stop size')
 MULTIPART_SEPARATOR = uuid.uuid4().hex.decode('ascii')
 COMPRESSIBLE_TYPES = {'application/json', 'application/javascript', 'application/xml', 'application/oebps-package+xml'}
-zlib, zlib2_err = plugins['zlib2']
-if zlib2_err:
-    raise RuntimeError('Failed to laod the zlib2 module with error: ' + zlib2_err)
-del zlib2_err
+if is_py3:
+    import zlib
+else:
+    zlib, zlib2_err = plugins['zlib2']
+    if zlib2_err:
+        raise RuntimeError('Failed to load the zlib2 module with error: ' + zlib2_err)
+    del zlib2_err
 
 
 def header_list_to_file(buf):  # {{{