diff --git a/gtsam_unstable/geometry/Similarity3.h b/gtsam_unstable/geometry/Similarity3.h
index 9e9ece8f5..85a773498 100644
--- a/gtsam_unstable/geometry/Similarity3.h
+++ b/gtsam_unstable/geometry/Similarity3.h
@@ -113,7 +113,7 @@ public:
     return s_;
   }
 
-  /// Convert to a rigid body pose
+  /// Convert to a rigid body pose (R, s*t)
   operator Pose3() const;
 
   /// Dimensionality of tangent space = 7 DOF - used to autodetect sizes