diff --git a/src/triacontagon/cumcount.py b/src/triacontagon/cumcount.py
index 5c88da6..164c784 100644
--- a/src/triacontagon/cumcount.py
+++ b/src/triacontagon/cumcount.py
@@ -24,7 +24,7 @@ def argunsort(s):
 
 def cumcount(a):
     n = torch.numel(a)
-    s = np.argsort(a.detach().cpu().numpy())
+    s = np.argsort(a.detach().cpu().numpy(), kind='mergesort')
     s = torch.tensor(s, device=a.device)
     i = argunsort(s)
     b = a[s]