diff --git a/tools/wptrunner/requirements_firefox.txt b/tools/wptrunner/requirements_firefox.txt
index 2021f550f4..39b5a3663d 100644
--- a/tools/wptrunner/requirements_firefox.txt
+++ b/tools/wptrunner/requirements_firefox.txt
@@ -8,4 +8,4 @@ mozprocess==1.0.0
 mozprofile==2.3.0
 mozrunner==7.5.1
 mozversion==2.1.0
-psutil==5.6.3
+psutil==5.6.6