The unusually large increase in stratospheric aerosol concentration resulting from the eruption of Agung in 1963 is shown to produce fictitious anomalies in the record of vertical ozone profiles determined from Umkehr observations at Aspendale, Australia. The anomalies are of sufficient magnitude that an empirical haze error to the profiles can be extracted from a comparison between seasonal averages of ozone profiles observed shortly after the Agung event and ozone profiles observed during periods of volcanic quiescence. Haze errors to the ozone profiles are also theoretically calculated for various models of vertical profiles of aerosols, ranging from relatively large concentrations of tropospheric aerosols to large c concentrations located exclusively in the stratosphere. It is shown that the theoretically determined haze errors are essentially of the same character as those determined empirically. Haze error corrections are applied to a long-term Umkehr record of north temperate upper stratospheric ozone concentration following Agung. The results imply that the anomalously low ozone concentrations in the upper stratosphere, noted after the eruption of Agung and Fuego in 1974, may not be real.