  A high-quality PrFeAsO$_{1-\delta}$ single crystal ($T_{\rm c}=44$ K) has
been investigated by the magnetic torque. Antiferromagnetism of the Pr$^{3+}$
ions was found to coexist with superconductivity in PrFeAsO$_{1-\delta}$ at
temperatures below $T_\mathrm{N}=14$ K. We predict a magnetic structure that is
not in accordance with earlier neutron studies performed using polycrystalline
nonsuperconducting specimens. As the temperature decreases, the superconducting
anisotropy $\gamma\sim 4$ of PrFeAsO$_{1-\delta}$ increases near $T_c$ and
tends to decrease slightly at lower temperatures.
