In accordance with various embodiments, systems and methods are provided which facilitate inferring immutability of variables. A compiler analyzes local variables within source code to determine whether they are immutable. In particular embodiments the compiler examines locations where each variable is assigned to determine whether the variable was definitely unassigned before the assignment. Because the compiler can infer whether a local variable is immutable, it is possible for the programmer to avoid using a keyword to expressly declare the local variable as immutable. Inferring immutability of variables, thus, maintains correctness of the compiled code while reducing the burden on the programmer.