diff --git a/pyproject.toml b/pyproject.toml
index 9808dbf709a..53b0d38567d 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -42,7 +42,7 @@ dev = [
   "ruff",
   "xarray[complete]",
 ]
-io = ["netCDF4", "h5netcdf", "scipy", 'pydap; python_version<"3.10"', "zarr", "fsspec", "cftime", "pooch"]
+io = ["netCDF4", "h5netcdf", "scipy", 'pydap; python_version<"3.10"', "zarr<3", "fsspec", "cftime", "pooch"]
 parallel = ["dask[complete]"]
 viz = ["matplotlib", "seaborn", "nc-time-axis"]