J.C. Penney Co Inc
Last week, Penney said Johnson, who oversees Apple's chain of stores, would become chief executive officer on November 1, reporting to Ullman, who would stay on as executive chairman.
But when Penney announced the appointment on Tuesday, it did not describe Ullman's role or say whether this would be part of a transition.
The Wall Street Journal reported over the weekend that Ullman, who has been CEO since 2004, would keep responsibility for stores, finance and accounting indefinitely.
On Monday, Penney specified that Johnson, who built Apple's stores into a chain of more than 300 in the last decade, would take over its merchandising and marketing functions on November 1.
Johnson, who has never been a CEO, will take over the remaining responsibilities after a three-month transition ending on February 1, Penney said.
A transition, while unusual, makes sense given Johnson's inexperience as a CEO and the arrival of a new chief financial officer in January, one analyst said.
They lost their CFO too and you need some continuity, said Morningstar analyst Paul Swinand.
Shares of Penney were up 9 cents at $34.38 in trading before the market opened.
(Reporting by Dhanya Skariachan and Phil Wahba; Editing by Lisa Von Ahn, Dave Zimmerman)