diff --git a/extensions/chaeo/annotators.py b/extensions/chaeo/annotators.py
index 10019d2b159978812ec53692e6c36251783f1833..145e1505cc1f2939ebf0b6fa0fda0959ca47fd8a 100644
--- a/extensions/chaeo/annotators.py
+++ b/extensions/chaeo/annotators.py
@@ -33,7 +33,6 @@ def draw_boxes_on_3d_image(yxcz_img, boxes, draw_full_depth=False, **kwargs):
     assert len(yxcz_img.shape) == 4
     nz = yxcz_img.shape[3]
     assert yxcz_img.shape[2] == 1
-    assert nz > 1
 
     annotated = np.zeros(yxcz_img.shape, dtype=yxcz_img.dtype)