We affirm the trial court’s denial of defendant’s petition for writ of mandamus naming Broward County Board of Commissioners and Broward Sheriff Ron Cochran as respondents. Defendant sought gain time pursuant to section 951.21, Florida Statutes (1995), which applies to gain time for good conduct of county prisoners.

Defendant was serving a fifteen-year prison term and was thus already a state prisoner in the custody of the Department of Corrections at the time of his transfer from prison to the Broward County Jail to attend an evidentiary hearing. Therefore, he was in only the temporary custody of the sheriff. Section 951.21 would not be applicable because he was not a county prisoner.

After a state prison sentence has been imposed, a defendant’s entitlement to any gain time, even for a temporary stay in county jail, is a decision that rests with the Department of Corrections. See Department of Corrections v. Mattress, 686 So.2d 740 (Fla. 5th DCA 1997). Our affirmance is without prejudice to defendant’s pursuing any remedies he may have with the Department of Corrections.