diff --git a/gtsam/geometry/geometry.i b/gtsam/geometry/geometry.i
index 3d816fc25a..095a350dd9 100644
--- a/gtsam/geometry/geometry.i
+++ b/gtsam/geometry/geometry.i
@@ -856,7 +856,7 @@ class Cal3_S2Stereo {
   gtsam::Matrix K() const;
   gtsam::Point2 principalPoint() const;
   double baseline() const;
-  Vector6 vector() const;
+  gtsam::Vector6 vector() const;
   gtsam::Matrix inverse() const;
 };