C++ / Uncrustify / Aligning base class specifications

Question

I am trying to configure Uncrustify to align the base classes to get comma under the colon:

class MyClass : public Base1
              , public Base2
              , public Base3 

The only output I can get is this:

class MyClass : public Base1
                , public Base2
                , public Base3

It is close, but it always adds 2 spaces to the other base classes. I am unable to find where these 2 spaces come from.