diff --git a/setup.py b/setup.py
index db4eda7..d01e8f6 100644
--- a/setup.py
+++ b/setup.py
@@ -34,6 +34,7 @@ def read(fname):
     "numpy>=1.16.1",
     "pathos",
     "scipy>=1.1.0",
+    "xs3d>=0.2.0",
   ],
   extras_require={
     'tif': [ 'tifffile' ],