diff --git a/tox.ini b/tox.ini
index 45259ef6..d88a7e8f 100644
--- a/tox.ini
+++ b/tox.ini
@@ -29,7 +29,8 @@ deps =
 [testenv]
 deps =
     {[base]deps}
-    {py27,py34,py35,py36,pypy,pypy3}: twisted
+    {py27,py35,py36,pypy,pypy3}: twisted
+    {py34}: twisted==19.2.0
 commands = coverage run --parallel -m pytest {posargs}
 
 ; Ensure test suite passes if no optional dependencies are present.