diff --git a/unittest/matrix.cpp b/unittest/matrix.cpp
index ce8a1c191aafb95e000b85e4eb3d111d04f70fd1..fd4ebae04b87b10d864e27bd0a3cc5e86bdb2763 100644
--- a/unittest/matrix.cpp
+++ b/unittest/matrix.cpp
@@ -81,6 +81,12 @@ MatrixDerived base(const Eigen::MatrixBase<MatrixDerived> & m)
   return m.derived();
 }
 
+template<typename MatrixDerived>
+MatrixDerived plain(const Eigen::PlainObjectBase<MatrixDerived> & m)
+{
+  return m.derived();
+}
+
 template<typename Scalar>
 Eigen::Matrix<Scalar,6,6> matrix6(const Scalar & value)
 {
@@ -123,6 +129,9 @@ BOOST_PYTHON_MODULE(matrix)
   
   bp::def("base", base<VectorXd>);
   bp::def("base", base<MatrixXd>);
+  
+  bp::def("plain", plain<VectorXd>);
+  bp::def("plain", plain<MatrixXd>);
 
   bp::def("matrix6", matrix6<double>);
 }
diff --git a/unittest/python/test_matrix.py b/unittest/python/test_matrix.py
index 5734eb92af3f25b6569cff7cb50a3f37f8e676c9..1b1ea6e739147df959056af916bee23827f11da3 100644
--- a/unittest/python/test_matrix.py
+++ b/unittest/python/test_matrix.py
@@ -36,6 +36,10 @@ Mref = np.reshape(np.array(range(64),np.double),[8,8])
 Mref_from_base = eigenpy.base(Mref)
 assert( np.array_equal(Mref,Mref_from_base) );
 
+# Test plain function
+Mref_from_plain = eigenpy.plain(Mref)
+assert( np.array_equal(Mref,Mref_from_plain) );
+
 if verbose: print("===> Matrix 8x8")
 M = Mref
 assert( np.array_equal(M,eigenpy.reflex(M,verbose)) );