diff --git a/.github/workflows/CI.yml b/.github/workflows/CI.yml
index d1b5eab..0be1896 100644
--- a/.github/workflows/CI.yml
+++ b/.github/workflows/CI.yml
@@ -15,7 +15,6 @@ jobs:
           - Core
         version:
           - '1.7'
-          - '1.9'
           - '1.10'
     steps:
       - uses: actions/checkout@v3
diff --git a/Project.toml b/Project.toml
index 7c138a5..0ba0252 100644
--- a/Project.toml
+++ b/Project.toml
@@ -15,7 +15,7 @@ Unitful = "1986cc42-f94f-5a68-af5c-568840ba703d"
 CoolProp = "0.1.0"
 DocStringExtensions = "^0.9"
 IfElse = "^0.1.1"
-ModelingToolkit = "^8"
+ModelingToolkit = "^9"
 SafeTestsets = "^0.0.1, 0.1"
 Unitful = "^1"
 julia = "^1.7"