The lambda-Pi calculus can be extended with rewrite rules to embed any other functional pure type system. The normalization and conserva-tivity properties of the embedding is an open problem. In this paper, we show that the embedding is conservative. We define an inverse translation into a pure type system completion and show that the completion is con-servative using the reducibility method. This result further justifies the use of the lambda-Pi calculus modulo rewriting as a logical framework.