diff --git a/conda_environment.yml b/conda_environment.yml
index 1d37d5a..dbc24c0 100644
--- a/conda_environment.yml
+++ b/conda_environment.yml
@@ -12,5 +12,5 @@ dependencies:
   - pip
   - pip:
     - CoolProp
-    - Cython
+    - Cython<3
     - quantities
\ No newline at end of file