The reaction CH3 + CH2O → CH4 + CHO has been studied in a shock tube in the temperature range 1170-1630 K, and its rate constant has been determined by kinetic modeling of the observed CO formation: k1 = 1015.0±0.4 exp(-11600 ± 1260/T). The results confirm earlier observations that the Arrhenius plot curves upward rather sharply at temperatures above 1000 K, although the effect appears less dramatic than reported previously. This nonlinearity cannot be rationalized by a standard transition-state model. However, the inclusion of a correction for quantum mechanical tunneling leads to an acceptable fit of the observed data over the entire experimental range (300-1700 K). A nonlinear least-squares fit to the calculated values covering 300-2000 K gives rise to k1 = 10-12.05T7.4 exp(483/T) cm3/mol·s).