diff --git a/gtsam/geometry/Cal3_S2.h b/gtsam/geometry/Cal3_S2.h
index b8cfda9ba..e3ae8859d 100644
--- a/gtsam/geometry/Cal3_S2.h
+++ b/gtsam/geometry/Cal3_S2.h
@@ -52,6 +52,7 @@ namespace gtsam {
       fx_(fx), fy_(fy), s_(s), u0_(u0), v0_(v0) {
     }
 
+    /// constructor from vector
     Cal3_S2(const Vector &d): fx_(d(0)), fy_(d(1)), s_(d(2)), u0_(d(3)), v0_(d(4)){}
 
 
diff --git a/gtsam/geometry/Cal3_S2Stereo.h b/gtsam/geometry/Cal3_S2Stereo.h
index 58fa1cd2d..811264967 100644
--- a/gtsam/geometry/Cal3_S2Stereo.h
+++ b/gtsam/geometry/Cal3_S2Stereo.h
@@ -49,6 +49,9 @@ namespace gtsam {
       K_(fx, fy, s, u0, v0), b_(b) {
     }
 
+    /// constructor from vector
+    Cal3_S2Stereo(const Vector &d): K_(d(0), d(1), d(2), d(3), d(4)), b_(d(5)){}
+
     /// @}
     /// @name Testable
     /// @{