In one example, an apparatus includes a video encoder configured to partition a block of video data into a first geometric partition and a second geometric partition using a geometric motion partition line, wherein the block comprises N×N pixels, divide the block of video data into four equally-sized, non-overlapping (N/2)×(N/2) sub-blocks, and encode at least one of the sub-blocks through which the geometric motion partition line passes using a transform size smaller than (N/2)×(N/2). The video encoder may determine transform sizes for the sub-blocks based on whether the geometric motion partition line passes through the sub-blocks. In one example, a video decoder may inverse transform the sub-blocks, and may determine transform sizes for the sub-blocks based on whether the geometric motion partition line passes through the sub-blocks.