diff --git a/matrix.cpp b/matrix.cpp
index c8e9279a..1b57f388 100644
--- a/matrix.cpp
+++ b/matrix.cpp
@@ -211,9 +211,11 @@ util::look_at (const util::point<3,T> eye,
 {
     CHECK (is_normalised (up));
 
-    const auto f = normalised (centre - eye);
-    const auto s = normalised (cross (f, up));
-    const auto u = cross (s, f);
+    const auto forward = normalised (centre - eye);
+    const auto side    = normalised (cross (forward, up));
+    const auto newup   = cross (side, forward);
+
+    const auto &f = forward, &s = side, &u = newup;
 
     const util::matrix4<T> rot {{
         { s.x, s.y, s.z, 0 },