keras-team/keras · error · ValueError

output_size must be an integer.

Error message

output_size must be an integer.

What it means

Error "output_size must be an integer." thrown in keras-team/keras.

Source

Thrown at keras/src/layers/rnn/rnn.py:248

        else:
            self.state_size = list(state_size)
            self.single_state = False

    def compute_output_shape(self, sequences_shape, initial_state_shape=None):
        batch_size = sequences_shape[0]
        length = sequences_shape[1]
        states_shape = []
        for state_size in self.state_size:
            if isinstance(state_size, int):
                states_shape.append((batch_size, state_size))
            elif isinstance(state_size, (list, tuple)):
                states_shape.append([(batch_size, s) for s in state_size])

        output_size = getattr(self.cell, "output_size", None)
        if output_size is None:
            output_size = self.state_size[0]
        if not isinstance(output_size, int):
            raise ValueError("output_size must be an integer.")
        if self.return_sequences:
            output_shape = (batch_size, length, output_size)
        else:
            output_shape = (batch_size, output_size)
        if self.return_state:
            return output_shape, *states_shape
        return output_shape

    def compute_mask(self, _, mask):
        # Time step masks must be the same for each input.
        # This is because the mask for an RNN is of size [batch, time_steps, 1],
        # and specifies which time steps should be skipped, and a time step
        # must be skipped for all inputs.
        mask = tree.flatten(mask)[0]
        output_mask = mask if self.return_sequences else None
        if self.return_state:
            state_mask = [None for _ in self.state_size]
            return [output_mask] + state_mask

View on GitHub (pinned to 7a34a03db6)

When it happens

Trigger: Thrown at keras/src/layers/rnn/rnn.py:248 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/27bf7c687baf278c. Report an issue: GitHub.