diff --git a/docs/Project.toml b/docs/Project.toml
index ae0d89dd3a..c542785859 100644
--- a/docs/Project.toml
+++ b/docs/Project.toml
@@ -40,7 +40,7 @@ Documenter = "1"
 DynamicQuantities = "^0.11.2, 0.12, 1"
 FMI = "0.14"
 FMIZoo = "1"
-ModelingToolkit = "10"
+ModelingToolkit = "10, 9"
 ModelingToolkitStandardLibrary = "2.19"
 NonlinearSolve = "3, 4"
 Optim = "1.7"