diff --git a/doc/rtd_environment.yml b/doc/rtd_environment.yml
index be2ff646c..295cc22de 100644
--- a/doc/rtd_environment.yml
+++ b/doc/rtd_environment.yml
@@ -27,7 +27,7 @@ dependencies:
   - sphinx-copybutton=0.5
   - pydata-sphinx-theme<0.15 # parallel-write-unsafe
   - numpydoc>=0.5
-  - sphinx-autodoc-typehints>=1.21.8=2.0
+  - sphinx-autodoc-typehints>=1.21.8,=2.0
   - typing_extensions
   # pip packages
   - pip