diff --git a/requirements.txt b/requirements.txt
index cd3ae5a20..6241d4d8e 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -2,7 +2,7 @@ numpy>=1.16.0
 scipy
 memory_profiler
 numba
-ase
+ase==3.21.0
 pymatgen
 nptyping
 nbsphinx