diff --git a/gtsam/nonlinear/ISAM2-inl.h b/gtsam/nonlinear/ISAM2-inl.h
index 6ff22c3a1..32a27f6fb 100644
--- a/gtsam/nonlinear/ISAM2-inl.h
+++ b/gtsam/nonlinear/ISAM2-inl.h
@@ -593,11 +593,11 @@ Values ISAM2<CONDITIONAL, GRAPH>::calculateEstimate() const {
 
 /* ************************************************************************* */
 template<class CONDITIONAL, class GRAPH>
-template<class KEY>
-typename KEY::Value ISAM2<CONDITIONAL, GRAPH>::calculateEstimate(const KEY& key) const {
+template<class VALUE>
+VALUE ISAM2<CONDITIONAL, GRAPH>::calculateEstimate(Key key) const {
   const Index index = getOrdering()[key];
   const SubVector delta = getDelta()[index];
-  return getLinearizationPoint()[key].retract(delta);
+  return theta_.at<VALUE>(key).retract(delta);
 }
 
 /* ************************************************************************* */
diff --git a/gtsam/nonlinear/ISAM2.h b/gtsam/nonlinear/ISAM2.h
index 4c8df2997..4a4bdea2c 100644
--- a/gtsam/nonlinear/ISAM2.h
+++ b/gtsam/nonlinear/ISAM2.h
@@ -390,8 +390,8 @@ public:
    * @param key
    * @return
    */
-  template<class KEY>
-  typename KEY::Value calculateEstimate(const KEY& key) const;
+  template<class VALUE>
+  VALUE calculateEstimate(Key key) const;
 
   /// @name Public members for non-typical usage
   //@{