# Error while creating augmented matrix: TypeError: unable to convert a to an integer

I am trying to create augmented matrix containing variables `a`

and `b`

, using the following code:

```
sage:
sage: u = Matrix([
....: [1, -1],
....: [2, 1]
....: ])
sage:
sage: var('a, b')
(a, b)
sage:
sage: w = vector([ a, b])
sage:
sage: u.augment(w, subdivide=True)
```

The last line, `u.augment(w, subdivide=True)`

, is giving me `TypeError: unable to convert a to an integer`

.