No, not the constant of integration, the variable of integration.  It is probably x. `Integral(stuff)` with just one argument only works if `stuff` only has one variable in it, which is not guaranteed here. 

```py
>>> Integral(x)
Integral(x, x)
>>> Integral(x*y)
Traceback (most recent call last):
  File "<ipython-input-21-d0158103d9ec>", line 1, in <module>
    Integral (x *y )
  File "/Users/aaronmeurer/Documents/Python/sympy/sympy/sympy/integrals/integrals.py", line 132, in __new__
    "specify variables of integration for %s" % function)
ValueError: specify variables of integration for x*y
```