diff --git a/ci/requirements/doc.yml b/ci/requirements/doc.yml
index e24adddf432..658a7d4e47b 100644
--- a/ci/requirements/doc.yml
+++ b/ci/requirements/doc.yml
@@ -23,6 +23,6 @@ dependencies:
   - rasterio>=1.1
   - seaborn
   - setuptools
-  - sphinx>=2.3
+  - sphinx=3.1
   - sphinx_rtd_theme>=0.4
   - zarr>=2.4