diff --git a/code_book/ch_opt_julia.md b/code_book/ch_opt_julia.md
index 8cac2bf..df0a19c 100644
--- a/code_book/ch_opt_julia.md
+++ b/code_book/ch_opt_julia.md
@@ -10,7 +10,7 @@ jupytext:
 kernelspec:
   display_name: Julia
   language: Julia
-  name: julia-1.9
+  name: julia-1.7
 ---
 
 # Chapter 3 - Optimal Flows (Julia Code)