  An excess of 511 keV photons has been detected from the central region of the
Milky Way. It has been suggested that the positrons responsible for this signal
could be produced through the Hawking evaporation of primordial black holes.
After evaluating the constraints from INTEGRAL, COMPTEL, and Voyager 1, we find
that black holes in mass range of $\sim(1-4)\times10^{16}$ g could potentially
produce this signal if they make up a small fraction of the total dark matter
density. If primordial black holes are responsible for the observed 511 keV
signal, then we should expect several hundred black holes to reside within the
Solar System. This class of scenarios should be testable with proposed
MeV-scale gamma-ray telescopes such as AMIGO or e-ASTROGAM.
