diff --git a/requirements.txt b/requirements.txt
index 78fff862f..ccff1d679 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,3 +1,4 @@
+monotonic==1.5
 aws-requests-auth>=0.3.0
 blist>=1.3.6
 boto3>=1.4.4