diff --git a/requirements.txt b/requirements.txt
index 95a8594415cd0b3f5f3f5596bf4aacf1b18b5233..76a713f32e287b96e697f3b4a5022792ac01ed60 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -36,5 +36,6 @@ scikit-learn == 0.22.2.post1
 sharedmem == 0.3.7 
 sphinx == 1.8.5
 tabulate == 0.8.6
+traitlets == 4.3.3
 unittest-xml-reporting == 3.0.2
 .