Missing Course Prerequisites

So I am taking a graduate-level course this semester on the theory of machine computing (Turing Machines, Halting Problem, etc.). The course catalog lists the prerequisites for this course to be only CSCI-2400 (Models of Computation). CSCI-2400 is the introductory course to this material and is generally for undergraduates. I took this class and did OK in it.

CSCI-2300 and MATH-2800 are the requirements for CSCI-2400. These courses are entitled "Data Structures and Algorithms" and "Introduction to Discrete Structures". I took CSCI-2400, but apparently was able to graduate with an undergraduate degree in computer science without taking MATH-2800. Now I find that I don't have the math background necessary to complete this graduate level course without really struggling, as much of the math is beyond my current knowledge.

How did my advisor, nay better, how did the institute let me graduate with a degree in Computer Science without at least attempting what many computer science folks would consider a very essential course? Easy - this course never used to be a requirement! Now it suddently is for the graduate school. I am so screwed. Clearly the degree I earned previously from this institute was not very worthwhile, as now I am unprepared for the institute's own graduate school!