diff --git a/jwst/assign_wcs/assign_wcs.py b/jwst/assign_wcs/assign_wcs.py
index c8426ce7c52..e5a6956a6c7 100644
--- a/jwst/assign_wcs/assign_wcs.py
+++ b/jwst/assign_wcs/assign_wcs.py
@@ -76,6 +76,8 @@ def load_wcs(input_model, reference_files=None, nrs_slit_y_range=None):
     wcs = WCS(pipeline)
     output_model.meta.wcs = wcs
     output_model.meta.cal_step.assign_wcs = "COMPLETE"
+    if output_model.meta.exposure.type.lower() == "nis_soss":
+        output_model.meta.wcs.bounding_box = mod.niriss_bounding_box(output_model)
     exclude_types = [
         "nrc_wfss",
         "nrc_tsgrism",
diff --git a/jwst/assign_wcs/niriss.py b/jwst/assign_wcs/niriss.py
index 69698ffad6c..ce905cf678f 100644
--- a/jwst/assign_wcs/niriss.py
+++ b/jwst/assign_wcs/niriss.py
@@ -102,12 +102,8 @@ def _niriss_order_bounding_box(input_model, order):
     bbox_y = np.array([-0.5, input_model.meta.subarray.ysize - 0.5])
     bbox_x = np.array([-0.5, input_model.meta.subarray.xsize - 0.5])
 
-    if order == 1:
-        return tuple(bbox_y), tuple(bbox_x)
-    elif order == 2:
-        return tuple(bbox_y), tuple(bbox_x)
-    elif order == 3:
-        return tuple(bbox_y), tuple(bbox_x)
+    if order in (1, 2, 3):
+        return tuple(bbox_x), tuple(bbox_y)
     else:
         raise ValueError(
             f"Invalid spectral order: {order} provided. Spectral order must be 1, 2, or 3."
@@ -131,7 +127,7 @@ def niriss_bounding_box(input_model):
     bbox = {(order,): _niriss_order_bounding_box(input_model, order) for order in [1, 2, 3]}
     model = input_model.meta.wcs.forward_transform
     return CompoundBoundingBox.validate(
-        model, bbox, slice_args=[("spectral_order", True)], order="F"
+        model, bbox, selector_args=[("spectral_order", True)], order="F"
     )