# Automatic Weights failing

I'm trying to rig a digitigrade model (which is already a challenge in itself), but I've hit an impasse where I try to generate Automatic Weights and it just fails, saying "Bone Heat Weighting: Failed to find a solution for one or more bones". How would I go about fixing this? I'll attach my Blender file.

For this instance, selecting all the vertices and doing Mesh->Vertices->Remove Doubles will solve it.