diff --git a/requirements.prophet.txt b/requirements.prophet.txt
index f2d78fde..e48001b2 100644
--- a/requirements.prophet.txt
+++ b/requirements.prophet.txt
@@ -1,2 +1,2 @@
 prophet==1.1.5
-pystan==2.19.1.1
+pystan==3.9.1