diff --git a/simulations/unity_poisson_sim/requirements.txt b/simulations/unity_poisson_sim/requirements.txt
index b4367e5..1aa6fc6 100644
--- a/simulations/unity_poisson_sim/requirements.txt
+++ b/simulations/unity_poisson_sim/requirements.txt
@@ -23,7 +23,7 @@ pexpect==4.6.0
 pickleshare==0.7.5
 prompt-toolkit==2.0.7
 ptyprocess==0.6.0
-Pygments==2.3.1
+Pygments==2.7.4
 pymongo==3.7.2
 pyparsing==2.3.0
 python-dateutil==2.7.5