Gas-filled hollow-core photonic crystal fibers are used to stabilize a fiber laser to the 13C2H2 P(16) (V1 + V3) transition at 1542 nm using saturated absorption. The fiber is encapsulated in glass cells for gas handling and compact free-space coupling, and packaged in a easy-to-use configuration. The system is showing a locking-point repeatability within 60 kHz with respect to a conventional acetylene vapor cell reference and an Allan deviation below 8 × 10−11 (τ/s)−1/2 for 1 < τ < 1000 s.