diff --git a/docs/source/usage/firstwrite.rst b/docs/source/usage/firstwrite.rst
index 927d9f650d..22141f5ef4 100644
--- a/docs/source/usage/firstwrite.rst
+++ b/docs/source/usage/firstwrite.rst
@@ -180,7 +180,7 @@ Python
 
    x_data = np.arange(
        150 * 300,
-       dtype=np.float
+       dtype=np.float64
    ).reshape(150, 300)