γ-ray light curve of PKS 0447−439 from August 2008 to December 2017 in the energy range between 100 MeV and 500 GeV in intervals of 30 days. The dotted line gives a fit with a constant flux. There is clear evidence for variability. Vertical error bars indicate the one-sigma error bars. The gray shaded regions show the 1σ, 3σ, and 5σ confidence intervals resulting from the fit with a constant function.