During the course of ionospheric heating experiments, an apparent electron density enhancement was observed at the European Incoherent Scatter Scientific Association (EISCAT). The enhancement extended over a wide range of altitudes, above the reflection altitude of the high-frequency pump wave. However, it remains open whether this enhancement actually corresponds to a true enhancement in electron density. Following the dispersion relation of ion acoustic waves, the frequency ratio of the enhanced ion line to the background ion line suggests that the profile of the effective ion mass might remain unchanged. Furthermore, the solar radio flux and ion drift velocity indicated no significant changes in the ion species and their densities. In conclusion, the electron density enhancement observed at EISCAT, might not in fact be a true enhancement.