roboflow/supervision · error · ValueError

Missing bndbox in Pascal VOC annotation.

Error message

Missing bndbox in Pascal VOC annotation.

What it means

Raised in detections_from_xml_obj when an <object> element in a Pascal VOC annotation has no <bndbox> child. Pascal VOC requires every object to carry a bndbox with xmin/ymin/xmax/ymax, so supervision refuses to guess coordinates and fails loudly. This protects downstream code that assumes every xyxy row is valid.

Source

Thrown at src/supervision/dataset/formats/pascal_voc.py:314

            updated list of class names, extended with the class names
            from the XML object. The Detections ``class_id`` is always an
            integer-dtype array, including the zero-``<object>`` (background)
            case where it is empty.
    """
    xyxy: list[list[int]] = []
    class_names: list[str] = []
    masks: list[npt.NDArray[np.bool_]] = []
    with_masks = force_masks or any(
        _with_poly_mask(obj) for obj in root.findall("object")
    )
    extended_classes = classes[:]
    for obj in root.findall("object"):
        class_name = _get_required_text(obj, "name")
        class_names.append(class_name)

        bbox = obj.find("bndbox")
        if bbox is None:
            raise ValueError("Missing bndbox in Pascal VOC annotation.")
        x1 = int(_get_required_text(bbox, "xmin"))
        y1 = int(_get_required_text(bbox, "ymin"))
        x2 = int(_get_required_text(bbox, "xmax"))
        y2 = int(_get_required_text(bbox, "ymax"))

        xyxy.append([x1, y1, x2, y2])

        object_mask: npt.NDArray[np.bool_] = np.zeros(
            (resolution_wh[1], resolution_wh[0]), dtype=bool
        )
        for polygon_element in obj.findall("polygon"):
            polygon = parse_polygon_points(polygon_element)
            # https://github.com/roboflow/supervision/issues/144
            polygon -= 1

            mask_from_polygon = polygon_to_mask(
                polygon=polygon,
                resolution_wh=resolution_wh,

View on GitHub (pinned to 7f254d9784)

Solutions

1. Open the annotation file for the failing image and find the <object> without <bndbox>.
2. Add a valid <bndbox><xmin>..<ymax></bndbox> block — if the object only has polygon points, compute the bounding box from the polygon min/max.
3. If the object is spurious, remove the whole <object> element.
4. If produced by a converter, fix or configure the converter to always emit bndbox, then re-export.

Example fix

<!-- before -->
<object>
  <name>dog</name>
  <polygon><x>10</x><y>10</y>...</polygon>
</object>
<!-- after: bndbox derived from polygon extremes -->
<object>
  <name>dog</name>
  <bndbox><xmin>10</xmin><ymin>10</ymin><xmax>180</xmax><ymax>220</ymax></bndbox>
  <polygon><x>10</x><y>10</y>...</polygon>
</object>

import xml.etree.ElementTree as ET
from pathlib import Path

def objects_missing_bndbox(xml_path: str) -> int:
    """Count <object> elements lacking <bndbox> in a VOC file."""
    root = ET.parse(xml_path).getroot()
    return sum(1 for obj in root.findall('object')
               if obj.find('bndbox') is None)

try:
    dataset = sv.DetectionDataset.from_pascal_voc(images_dir, ann_dir)
except ValueError as e:
    if 'Missing bndbox' in str(e):
        raise RuntimeError(f'Corrupt VOC annotation: {e}. Repair or remove the file.') from e
    raise

When it happens

Trigger: Loading a Pascal VOC dataset (DetectionDataset.from_pascal_voc) where at least one <object> element lacks a <bndbox> subtree — e.g. hand-edited XML, segmentation-only exports, or converter tools that omit bndbox.

Common situations: Annotations exported by nonstandard tools (some segmentation annotators write only <polygon>); manual XML edits that deleted the bndbox; truncated XML written by a crashing exporter; datasets mixing VOC-like dialects.

Related errors

• Failed to parse XML root from {annotation_path}
• Missing polygon coordinate value in Pascal VOC.
• Missing '{tag}' in Pascal VOC annotation.
• Could not read image from path: {image_path}
• LabelMe shape of type {shape_type} is missing the required {

AI-assisted analysis of roboflow/supervision@7f254d9784 (2026-08-15). Data as JSON: /api/errors/ce051d08c045b62d. Report an issue: GitHub.