diff --git a/include/eigenpy/quaternion.hpp b/include/eigenpy/quaternion.hpp
index eca40145fc12acd58643320b9edb7e107a015805..d1462f2e8c1c1c06ecd29ae01b57a19198899e08 100644
--- a/include/eigenpy/quaternion.hpp
+++ b/include/eigenpy/quaternion.hpp
@@ -309,7 +309,7 @@ namespace eigenpy
       
       // Cast to Eigen::QuaternionBase and vice-versa
       bp::implicitly_convertible<Quaternion,QuaternionBase >();
-      bp::implicitly_convertible<QuaternionBase,Quaternion >();
+//      bp::implicitly_convertible<QuaternionBase,Quaternion >();
     }
 
   };