diff --git a/pvanalytics/features/shading.py b/pvanalytics/features/shading.py
index 08ea73ed..d76977ea 100644
--- a/pvanalytics/features/shading.py
+++ b/pvanalytics/features/shading.py
@@ -113,7 +113,7 @@ def _prepare_images(ghi, clearsky, daytime, interval):
     ghi_image = pd.DataFrame(cloudless_image).interpolate(
         axis=0,
         limit_direction='both'
-    ).to_numpy()
+    ).to_numpy().copy()
     # set night to nan
     ghi_image[~_to_image(daytime.to_numpy(), image_width)] = np.nan
     return (
@@ -365,7 +365,7 @@ def fixed(ghi, daytime, clearsky, interval=None, min_gradient=2):
     threshold = gradient > min_gradient  # binary image of wire candidates
 
     # From here we CAN use skimage because we are working with binary images.
-    three_minute_mask = morphology.rectangle(1, 3)
+    three_minute_mask = morphology.footprint_rectangle((1, 3))
     wires = morphology.remove_small_objects(
         morphology.binary_closing(threshold, three_minute_mask),
         min_size=200,