diff --git a/gtsam/geometry/Rot3Q.cpp b/gtsam/geometry/Rot3Q.cpp
index 23c4dc5f0..4a13bfeee 100644
--- a/gtsam/geometry/Rot3Q.cpp
+++ b/gtsam/geometry/Rot3Q.cpp
@@ -51,7 +51,7 @@ namespace gtsam {
 
   /* ************************************************************************* */
   Rot3::Rot3(const Matrix& R) :
-      quaternion_(R) {}
+      quaternion_(Matrix3(R)) {}
 
 //  /* ************************************************************************* */
 //   Rot3::Rot3(const Matrix3& R) :