diff --git a/tf_pwa/fit_improve.py b/tf_pwa/fit_improve.py
index 0e700d8..d31131f 100644
--- a/tf_pwa/fit_improve.py
+++ b/tf_pwa/fit_improve.py
@@ -98,7 +98,7 @@ def fmin_bfgs_f(
     Delta=10.0,
     maxiter=None,
     callback=None,
-    norm_ord=np.Inf,
+    norm_ord=np.inf,
     **_kwargs
 ):
     """test BFGS with nonmonote line search"""