diff --git a/gtsam/base/Vector.cpp b/gtsam/base/Vector.cpp
index ce3f0a7b0..a9a0efa36 100644
--- a/gtsam/base/Vector.cpp
+++ b/gtsam/base/Vector.cpp
@@ -204,11 +204,6 @@ Vector ediv_(const Vector &a, const Vector &b) {
   return c;
 }
 
-/* ************************************************************************* */
-double sum(const Vector &a) {
-  return a.sum();
-}
-
 /* ************************************************************************* */
 double norm_2(const Vector& v) {
   return v.norm();
diff --git a/gtsam/base/Vector.h b/gtsam/base/Vector.h
index 5bb732f5c..7e9214789 100644
--- a/gtsam/base/Vector.h
+++ b/gtsam/base/Vector.h
@@ -228,13 +228,6 @@ GTSAM_EXPORT Vector ediv(const Vector &a, const Vector &b);
  */
 GTSAM_EXPORT Vector ediv_(const Vector &a, const Vector &b);
 
-/**
- * sum vector elements
- * @param a vector
- * @return sum_i a(i)
- */
-GTSAM_EXPORT double sum(const Vector &a);
-
 /**
  * Calculates L2 norm for a vector
  * modeled after boost.ublas for compatibility
@@ -343,9 +336,9 @@ GTSAM_EXPORT Vector concatVectors(size_t nrVectors, ...);
 #ifdef GTSAM_ALLOW_DEPRECATED_SINCE_V4
 GTSAM_EXPORT inline Vector emul(const Vector &a, const Vector &b) {assert (b.size()==a.size()); return a.cwiseProduct(b);}
 GTSAM_EXPORT inline Vector reciprocal(const Vector &a) {return a.array().inverse();}
+GTSAM_EXPORT inline double sum(const Vector &a){return a.sum();}
 #endif
 
-
 } // namespace gtsam
 
 #include <boost/serialization/nvp.hpp>