diff --git a/requirements.txt b/requirements.txt
index 7e61f94..c4377a5 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -10,4 +10,4 @@ numpy>=1.16.1
 pathos
 pytest
 scipy>=1.1.0
-xs3d
\ No newline at end of file
+xs3d>=1.2.0,<2
\ No newline at end of file