diff --git a/.github/workflows/documentation.yml b/.github/workflows/documentation.yml
index f9c20abde..404de46ff 100644
--- a/.github/workflows/documentation.yml
+++ b/.github/workflows/documentation.yml
@@ -16,7 +16,7 @@ jobs:
       - uses: actions/checkout@v2
       - uses: julia-actions/setup-julia@v1
         with:
-          version: '1.9'
+          version: '1'
       - name: Install dependencies
         run: julia --project=docs/ -e 'using Pkg; Pkg.develop(PackageSpec(path=pwd())); Pkg.instantiate()'
       - name: Build and deploy
diff --git a/docs/Project.toml b/docs/Project.toml
index 7d5632a39..2f94ea2f6 100644
--- a/docs/Project.toml
+++ b/docs/Project.toml
@@ -16,3 +16,4 @@ JuMP = "1"
 LinearAlgebra = "1.6"
 Logging = "1.6"
 Plots = "1"
+ModelingToolkit = "9"