That was the law prior to 1999 (Soliman, supreme court 1993). Tax Relief Act of 1997 relaxed Code Sec. 280A(c)(1). :
"For purposes of subparagraph (A) , the term “principal place of business” includes a place of business which is used by the taxpayer for the administrative or management activities of any trade or business of the taxpayer if there is no other fixed location of such trade or business where the taxpayer conducts substantial administrative or management activities of such trade or business."