diff --git a/setup.py b/setup.py
index a7679e6..fcec5b1 100755
--- a/setup.py
+++ b/setup.py
@@ -289,6 +289,7 @@ install_requires = [
     'decorator',
     'pickleshare',
     'simplegeneric>0.8',
+    'traitlets',
 ]
 
 # add platform-specific dependencies