diff --git a/gtsam_unstable/slam/TransformBtwRobotsUnaryFactorEM.h b/gtsam_unstable/slam/TransformBtwRobotsUnaryFactorEM.h
index 35010cdc6..2f0b2c7a8 100644
--- a/gtsam_unstable/slam/TransformBtwRobotsUnaryFactorEM.h
+++ b/gtsam_unstable/slam/TransformBtwRobotsUnaryFactorEM.h
@@ -372,7 +372,7 @@ namespace gtsam {
       const T& p2 = values.at<T>(keyB_);
 
       Matrix H1, H2;
-      T hx = p1.between(p2, H1, H2); // h(x)
+      p1.between(p2, H1, H2); // h(x)
 
       Matrix H;
       H.resize(H1.rows(), H1.rows()+H2.rows());