diff --git a/sumo/electronic_structure/optics.py b/sumo/electronic_structure/optics.py
index e900a94d..2365a08c 100644
--- a/sumo/electronic_structure/optics.py
+++ b/sumo/electronic_structure/optics.py
@@ -256,7 +256,7 @@ def kkr(de, eps_imag, cshift=1e-6):
     eps_imag = np.array(eps_imag)
     nedos = eps_imag.shape[0]
     cshift = complex(0, cshift)
-    w_i = np.arange(0, (nedos - 0.5) * de, de, dtype=np.complex_)
+    w_i = np.arange(0, (nedos - 0.5) * de, de, dtype=np.complex128)
     w_i = np.reshape(w_i, (nedos, 1, 1))
 
     def integration_element(w_r):