Niger state governor appoints speaker instead of deputy as acting governor while he performs Hajj

I wonder, is this constitutional?

There are reports that Niger State governor, Dr. Mu'azu Babangida Aliyu has ignored his deputy, Hon. Ahmed Musa Ibeto and appointed the Speaker of the State House of Assembly, Hon. Adamu Usman to oversee the affairs of the state in a capacity of acting governor while he performs the Lesser Hajj (Umrah).

Last week Wednesday, the governor had ordered his deputy out of the weekly state executive council meeting and vowed not to have anything to do with him. The governor accused Ibeto, who defected from the ruling Peoples Democratic Party to All Progressives Congress (APC) last month of insulting him at APC campaign rallies.

The governor who will be away from  February 19th to 29th wrote to the Speaker in a letter he personally signed and sent to the state assembly to inform them of his intention to travel to the Kingdom of Saudi Arabia for Umrah.

The letter with reference number GHNS/13/72 dated 17th February, 2015 reads in part, "I wish to inform Mr. Speaker, that I intend to travel to the Kingdom of Saudi Arabia to perform the Lesser Hajj between 19th-26th Febuary, 2015. In my absence, the Honourable Speaker,  Niger State House of Assembly, Rt. Honourable Adamu Usman will over see my schedules as the acting governor."