keras-team/keras · error · ValueError

The channel dimension of the inputs (last axis) should be de

Error message

The channel dimension of the inputs (last axis) should be defined. Found None. Full input shape received: input_shape={inputs_shape}

What it means

Error "The channel dimension of the inputs (last axis) should be defined. Found None. Full input shape received: input_shape={inputs_shape}" thrown in keras-team/keras.

Source

Thrown at keras/src/layers/rnn/conv_lstm.py:178

        self.dropout_mask_count = 4
        self.input_spec = InputSpec(ndim=rank + 2)
        self.state_size = -1  # Custom, defined in methods

    def build(self, inputs_shape, states_shape=None):
        if self.data_format == "channels_first":
            channel_axis = 1
            self.spatial_dims = inputs_shape[2:]
        else:
            channel_axis = -1
            self.spatial_dims = inputs_shape[1:-1]
        if None in self.spatial_dims:
            raise ValueError(
                "ConvLSTM layers only support static "
                "input shapes for the spatial dimension. "
                f"Received invalid input shape: input_shape={inputs_shape}"
            )
        if inputs_shape[channel_axis] is None:
            raise ValueError(
                "The channel dimension of the inputs (last axis) should be "
                "defined. Found None. Full input shape received: "
                f"input_shape={inputs_shape}"
            )
        self.input_spec = InputSpec(
            ndim=self.rank + 3, shape=(None,) + inputs_shape[1:]
        )

        input_dim = inputs_shape[channel_axis]
        self.input_dim = input_dim
        self.kernel_shape = self.kernel_size + (input_dim, self.filters * 4)
        recurrent_kernel_shape = self.kernel_size + (
            self.filters,
            self.filters * 4,
        )

        self.kernel = self.add_weight(
            shape=self.kernel_shape,

View on GitHub (pinned to 7a34a03db6)

When it happens

Trigger: Thrown at keras/src/layers/rnn/conv_lstm.py:178 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of keras-team/keras@7a34a03db6 (2026-08-25). Data as JSON: /api/errors/7d7eceeecb052fb4. Report an issue: GitHub.