diff --git a/y2018/control_loops/python/extended_lqr.py b/y2018/control_loops/python/extended_lqr.py
index e19ee8f..a2a31af 100755
--- a/y2018/control_loops/python/extended_lqr.py
+++ b/y2018/control_loops/python/extended_lqr.py
@@ -85,6 +85,7 @@
     Returns:
       numpy.matrix(1, 1), The quadratic cost of being at X
     """
+        print('TODO(austin): S -> X.T * S * X, need to fix if we care')
         return 0.5 * X.T * self.S * X
 
     def cost(self, X, U):