diff --git a/docs/requirements.txt b/docs/requirements.txt
index 62b50ec..40f2e75 100644
--- a/docs/requirements.txt
+++ b/docs/requirements.txt
@@ -1,2 +1,3 @@
 autodoc_pydantic>=2.2.0
-sphinx-rtd-theme>=3.0.2
\ No newline at end of file
+sphinx-rtd-theme>=3.0.2
+czml3