In one example, an apparatus for coding video data comprises a video coder configured to obtain a motion vector for predicting a video block with a non-4:2:0 chroma format, determine a video block size for the video block, modify the motion vector to generate a modified motion vector for obtaining samples of at least one reference picture with which to predict the video block if the video block size meets a size criterion, and generate a prediction block for the video block using the samples of the at least one reference picture and the modified motion vector.