# Bug? Polynomial variable name matters

The following calculation of an intersection of curves over `QQbar`

raises an error within Singular on Sage v9.2.

```
P.<a, y, z> = ProjectiveSpace(QQbar, 2)
f = a^3 + z^3
C = Curve(f)
g = (a + y)^3 + z^3
D = Curve(g)
print(C.intersection_points(D))
```

It does work when replacing the variable name `a`

by `x`

.

I assume this is a bug but could not trace it down to the internals of `rational_points`

and the Singular interface. The variables `b`

and `d`

work, whereas `c`

raises a different error. Does anyone know more about that? Is it already fixed in the newer versions? Should I post this as a ticket on https://trac.sagemath.org?