In this paper, we introduce a new type system based on linear typing, and show how it can be incorporated in a concurrent programming language to track ownership of promises. By tracking write operations on each promise, the language is able to guarantee exactly one write operation is ever performed on any given promise. This language thus precludes a number of common bugs found in promise-based programs, such as failing to write to a promise and writing to the same promise multiple times. We also present an implementation of the language, complete with an efficient type checking algorithm and high-level programming constructs. This language serves as a safer platform for writing high-level concurrent code.