diff --git a/extern/libmv/libmv/multiview/homography.cc b/extern/libmv/libmv/multiview/homography.cc
index ce533a3ead2..a7679c33bbf 100644
--- a/extern/libmv/libmv/multiview/homography.cc
+++ b/extern/libmv/libmv/multiview/homography.cc
@@ -209,8 +209,8 @@ class HomographySymmetricGeometricCostFunctor {
     return true;
   }
 
-  const Vec2 x_;
-  const Vec2 y_;
+  const Vec2 &x_;
+  const Vec2 &y_;
 };
 
 // Termination checking callback used for homography estimation.