In Pre-release 5 of Minecraft Beta 1.9, the dirt texture had a slight change. This affected all textures that use dirt as a base in Minecraft, but the Mycelium side (which was fixed recently) and this - Options Background texture which was never changed. Here is a GIF comparison of how it is and how it should be: "O" stands for "Old/Current", and "N" for "New - Fixed version".