Redstone "wires" do not visually connect when placed in straight lines

When redstone dust is placed adjacent to another piece of redstone it does not connect, but just forms both into a parallel line. This does not appear to affect the functioning of the circuit or signal conduction. This happens regardless of North-South / East-West adjacency. This only occurs when a segment of redstone dust has only one neighbour; all multi-neighbour redstone textures are correct.