open-mmlab/mmdetection · error · ValueError

There is not post_norm in {name}

Error message

There is not post_norm in {name}

What it means

GroundingDinoTransformerDecoder raises ValueError if post_norm_cfg is not None. Like the deformable decoder, Grounding DINO's decoder handles normalization internally and explicitly rejects a configured post-norm.

Source

Thrown at mmdet/models/layers/transformer/grounding_dino_layers.py:266

                query_pos=query_pos,
                reference_points=reference_points,
                spatial_shapes=spatial_shapes,
                level_start_index=level_start_index,
                key_padding_mask=key_padding_mask)
        return output, memory_text


class GroundingDinoTransformerDecoder(DinoTransformerDecoder):

    def _init_layers(self) -> None:
        """Initialize decoder layers."""
        self.layers = ModuleList([
            GroundingDinoTransformerDecoderLayer(**self.layer_cfg)
            for _ in range(self.num_layers)
        ])
        self.embed_dims = self.layers[0].embed_dims
        if self.post_norm_cfg is not None:
            raise ValueError('There is not post_norm in '
                             f'{self._get_name()}')
        self.ref_point_head = MLP(self.embed_dims * 2, self.embed_dims,
                                  self.embed_dims, 2)
        self.norm = nn.LayerNorm(self.embed_dims)

View on GitHub (pinned to cfd5d3a985)

Solutions

1. Set post_norm_cfg=None in the decoder config
2. Audit _base_ config files for a stray post_norm_cfg and override it

Example fix

# before
post_norm_cfg=dict(type='LN')
# after
post_norm_cfg=None

assert decoder_cfg.get('post_norm_cfg', None) is None

When it happens

Trigger: Building GroundingDinoTransformerDecoder with a config inherited from a DETR-style base that sets post_norm_cfg (e.g. dict(type='LN')).

Common situations: Config inheritance from DETR/DAB-DETR baselines; porting configs between detection transformer variants.

Understand the failure class

Background: "Invalid value" and "allowed values are" config errors: what your library rejected and how to fix it — this error's family across 41 libraries.

Related errors

• Unknown query_scale_type: {}
• There is not post_norm in {name}
• Invalid text mode "{self.text_mode}".
• The type of frame_range must be int or list.
• results does not contain masks.

AI-assisted analysis of open-mmlab/mmdetection@cfd5d3a985 (2026-08-27). Data as JSON: /api/errors/81ee88bacc6736df. Report an issue: GitHub.