diff --git a/README.md b/README.md
index 218cecc6f..ae1ae42e1 100644
--- a/README.md
+++ b/README.md
@@ -13,7 +13,7 @@ This analysis repository presumes that the following python packages are availab
  * scipy
  * matplotlib
  * netCDF4
- * xarray
+ * xarray ≥ 0.9.1
  * dask
  * bottleneck
  * basemap