Warning usng facsum to factor specific terms



Hi,

When trying to factor out specific terms from an expression using facsum, I
get a warning message and the correct answer.

(%i44) facsum(a*b+b*c+a*c, a);
Warning - you are redefining the MACSYMA function INTERSECTION
(%o44)                                  A (C + B) + B C

Why does maxima issue this warning and should I be concerned about it at
all?

Julian