diff --git a/testing/mozharness/requirements.txt b/testing/mozharness/requirements.txt
index 571ce421e4..9314abfee5 100644
--- a/testing/mozharness/requirements.txt
+++ b/testing/mozharness/requirements.txt
@@ -8,7 +8,7 @@ dulwich==0.8.7
 hg-git==0.4.0
 logilab-astng==0.24.2
 logilab-common==0.59.0
-mercurial==3.7.3
+mercurial ~> 4.1.3
 mock==1.0.1
 nose==1.2.1
 ordereddict==1.1