diff --git a/requirements.txt b/requirements.txt
index 6788c6c2..85e6ac6c 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -3,6 +3,7 @@ intervaltree
 numpy
 progressbar2
 pyjson5
+pyyaml
 scipy
 sympy
 yapf==0.24.0