diff --git a/autogalaxy/profiles/mass/dark/nfw.py b/autogalaxy/profiles/mass/dark/nfw.py
index 9963211d..f921a60f 100644
--- a/autogalaxy/profiles/mass/dark/nfw.py
+++ b/autogalaxy/profiles/mass/dark/nfw.py
@@ -419,5 +419,5 @@ def potential_2d_from(self, grid: aa.type.Grid2DLike, xp=np, **kwargs):
     @staticmethod
     def potential_func_sph(eta, xp=np):
         return ((xp.log(eta.array / 2.0)) ** 2) - (
-            xp.arctanh(np.sqrt(1 - eta.array**2))
+            xp.arctanh(xp.sqrt(1 - eta.array**2))
         ) ** 2