Index: include/numerics/petsc_vector.h
===================================================================
--- include/numerics/petsc_vector.h	(revision 4557)
+++ include/numerics/petsc_vector.h	(working copy)
@@ -502,7 +502,7 @@
    * not required in user-level code. Just don't do anything crazy like
    * calling VecDestroy()!
    */
-  Vec vec () { libmesh_assert (_vec != NULL); return _vec; }
+  Vec vec () const { libmesh_assert (_vec != NULL); return _vec; }
 
 
   
Index: include/numerics/petsc_matrix.h
===================================================================
--- include/numerics/petsc_matrix.h	(revision 4557)
+++ include/numerics/petsc_matrix.h	(working copy)
@@ -327,7 +327,7 @@
    * not required in user-level code. Just don't do anything crazy like
    * calling MatDestroy()!
    */
-  Mat mat () { libmesh_assert (_mat != NULL); return _mat; }
+  Mat mat () const { libmesh_assert (_mat != NULL); return _mat; }
 
 protected: