diff --git a/etc/requirements.txt b/etc/requirements.txt
index ac4c2b88..7ffa9527 100644
--- a/etc/requirements.txt
+++ b/etc/requirements.txt
@@ -55,4 +55,6 @@ toolz==0.7.4
 # Asset writer and finder
 sqlalchemy==1.0.8
 
+# for intervaltree
+sortedcontainers==1.4.4
 intervaltree==2.1.0