Strange loop

[babbutycoon]

ethash/src/libethash/internal.c

Line 198 in f5f0a8b

for (uint32_t w = 0; w != MIX_WORDS; ++w) {

How come the loop is for (uint32_t w = 0; w != MIX_WORDS; ++w)??
The #define for MIX_WORDS is 32. whereas the union node accessed via word is a max of 16.
Am i not looking at this right or is it actually a bug?