diff --git a/server/requirements.txt b/server/requirements.txt
index 1cfdf7d5..4947db35 100644
--- a/server/requirements.txt
+++ b/server/requirements.txt
@@ -2,13 +2,13 @@ anndata>=0.7.0
 boto3>=1.12.18
 click>=7.1.2
 fastobo>=0.6.1
-Flask>=1.0.2
+Flask>=1.0.2,<2.0.0 # Flask 2.0 is not compatible with the latest version of Flask-RESTful (0.3.8)
 Flask-Compress>=1.4.0
 Flask-Cors>=3.0.6
 Flask-RESTful>=0.3.6
 flask-server-timing>=0.1.2
 flask-talisman>=0.7.0
-flatbuffers>=1.11.0
+flatbuffers>=1.11.0,<2.0.0 # cellxgene is not compatible with 2.0.0. Requires migration
 flatten-dict>=0.2.0
 fsspec>=0.4.4,<0.8.0
 gunicorn>=20.0.4