diff --git a/requirements.txt b/requirements.txt
index ec744d6b..706560d3 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -2,7 +2,7 @@ xarray>=0.18,<2024.3
 scipy>=1.5
 netCDF4>=1.5.3 #<1.5.9
 toolz>=0.8.2
-erddapy>0.8
+erddapy>0.8  # erddapy >= 2.2.1 only compatible with python >= 3.10
 fsspec>=0.8
 aiohttp>=3.7
 packaging>=20.4  # Using 'version' to make API compatible with several fsspec releases