diff --git a/overreact/_misc.py b/overreact/_misc.py
index 6ae6af7..de823ca 100644
--- a/overreact/_misc.py
+++ b/overreact/_misc.py
@@ -15,6 +15,14 @@
 import overreact as rx
 from overreact import _constants as constants
 
+def make_hashable(obj):
+    if isinstance(obj, np.ndarray):
+        return tuple(obj.ravel())
+    elif isinstance(obj, (list, set)):
+        return tuple(map(make_hashable, obj))
+    else:
+        return obj
+    
 def copy_unhashable(maxsize=128, typed=False): 
     """Creates a copy of the arrays received by lru_cache and make them hashable, therefore maintaining the arrays to be passed and caching prototypes of those arrays.
     
diff --git a/overreact/coords.py b/overreact/coords.py
index 3e2f545..2c1467e 100644
--- a/overreact/coords.py
+++ b/overreact/coords.py
@@ -1682,7 +1682,7 @@ def gyradius(atommasses, atomcoords, method="iupac"):
         raise ValueError(msg)
     
 
-@rx._misc.copy_unhashable
+@rx._misc.copy_unhashable()
 def inertia(atommasses, atomcoords, align=True):
     r"""Calculate primary moments and axes from the inertia tensor.