diff --git a/requirements-py3.txt b/requirements-py3.txt
index 08ccf1958..690e7e915 100644
--- a/requirements-py3.txt
+++ b/requirements-py3.txt
@@ -1,4 +1,4 @@
-Twisted >= 15.5.0
+Twisted>=15.5.0,<=16.6
 lxml>=3.2.4
 pyOpenSSL>=0.13.1
 cssselect>=0.9
diff --git a/requirements.txt b/requirements.txt
index ad9226e87..44bf7bcd2 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,5 +1,5 @@
-Twisted>=10.0.0
-lxml
+Twisted>=10.0.0,<=16.6
+lxml>=2.3
 pyOpenSSL
 cssselect>=0.9
 w3lib>=1.14.2
diff --git a/setup.py b/setup.py
index 000d84614..3911ee2bd 100644
--- a/setup.py
+++ b/setup.py
@@ -41,10 +41,10 @@ setup(
         'Topic :: Software Development :: Libraries :: Python Modules',
     ],
     install_requires=[
-        'Twisted>=10.0.0',
+        'Twisted>=10.0.0,<=16.6',
         'w3lib>=1.14.2',
         'queuelib',
-        'lxml',
+        'lxml>=2.3',
         'pyOpenSSL',
         'cssselect>=0.9',
         'six>=1.5.2',