That could be a unit requirement. If t.u. gives you credit for it, I would fight retaking it. Go talk to your class advisor, and if he's making you, go ask your next year's advisor what his take is. I should have gotten PRBed for not finishing calc 2 by the end of my sophomore year, but he was just like finish it this summer and you're fine. My junior year, my advisor called me in and asked me when I planned on taking my computer science class. I showed him the unit instruction i got my freshman year that counted the maple lab portion of calc 1 counted towards the requirement. He had a different, newer, instruction, but since he was a cool guy (and a history major) he marked me off as being complete per THAT instruction since I came into the program when that requirement was in effect. Bottom line: see what your advisor says, since he's the one who will decide. If he tells you you're good to go, ask him to write something to that effect in your jacket, so you don't get called in two weeks before graduating and bitched at for "not completing" the requirement. Didn't happen to me from NROTC, but I almost got my required minor denied due to a glitch in the computer system and it not being meshed up with the minor agreement that I signed. I showed them the note from my minor advisor that I had kept for two years saying I was fine and they had to accept it.
I don't think it's a unit only requirement, I think it might be a requirement from the Navy. I had a 5 on AP Calc AB but I had to redo calc. I did the first two semesters over again, but I subsequently found out I actually only needed to redo semester 2 :icon_rage But on the plus side I got 2 easy A's on my transcript.