The gain of silicon photomultipliers (SiPMs) increaseswith bias voltage V_{\mathbf{bias}} and decreases with temperature T. For stable operation, the gain G needs to be kept constant, especially in large detector systems such as an analog hadron calorimeter operating with 10^{\mathbf{6}} SiPMs 1. Variations of the ambient temperature and heat produced by electronics typically induces gain changes in SiPMs. The method of keeping the gain constant consists of adjusting V_{\mathbf{bias}}when T changes. This requires knowledge of dV/dT, which we obtain from measurements of dG/dV dG/dT. Assuming a linear dependence of G versus V_{\mathbf{bias\, }}and T yields constant values for dG/dV versus T and dG/dT versus V_{\mathbf{bias}} and in turn a constant value for dV/dT. We built a bias voltage regulator that adjusts V_{\mathbf{bias}}. We tested gain stability of 30 SiPMs from three manufacturers (Hamamatsu, KETEK, CPTA) in the temperature range of 1 ^{circ}\mathrm{C}- 50 ^{circ}\mathrm{C} using a climate chamber at CERN. While six of the Hamamatsu SiPMs have trenches to suppress cross talk, all other SiPMs have no trenches. We consider gain stabilization successful if the gain change in 20 ^{circ}\mathrm{C}- 30 ^{circ}\mathrm{C} is smaller than ± 0.5%. In our tests, we stabilized four SiPMs simultaneously with one dV/dT setting. This work was accomplished in the framework of AIDA2020. Do not cite references in the abstract. Do not delete the blank line immediately above the abstract; it sets the footnote at the bottom of this column.