diff --git a/cruft/util/vector.hpp b/cruft/util/vector.hpp
index 05181fc3..4457f11b 100644
--- a/cruft/util/vector.hpp
+++ b/cruft/util/vector.hpp
@@ -66,7 +66,7 @@ namespace cruft {
     T
     cross (vector<2,T> a, vector<2,T> b)
     {
-        return a[0] * b[1] - a[1] * b[0];
+        return a.x * b.y - a.y * b.x;
     }