ValueError: Error when checking target: expected embedding_1 to have shape (55, 50) but got array with shape (55, 16)

batch_size=16
        words = 20000
        units = 50
        tokens_per_sentence= 55

        print (x.shape)

        x_shape =  x.shape

        model = Sequential()

        model.add(Embedding(words, units,input_length=tokens_per_sentence, batch_size=batch_size , input_shape=x_shape[1:]))

        model.compile(optimizer='adam', loss='categorical_crossentropy', metrics=['accuracy'])

        model.train_on_batch(x, y)