diff --git a/src/vector.c b/src/vector.c
index 64b247d..15711f8 100644
--- a/src/vector.c
+++ b/src/vector.c
@@ -1190,9 +1190,9 @@ hamming_distance(PG_FUNCTION_ARGS)
 
 	CheckBitLengths(VARBITLEN(a), VARBITLEN(b));
 
+	/* TODO Improve performance */
 	for (uint32 i = 0; i < VARBITBYTES(a); i++)
 		distance += pg_number_of_ones[ax[i] ^ bx[i]];
 
-	/* TODO Decide on return type */
 	PG_RETURN_FLOAT8((double) distance);
 }