diff --git a/include/armadillo_bits/SpBase_bones.hpp b/include/armadillo_bits/SpBase_bones.hpp
index 30f34c95..2f2c4249 100644
--- a/include/armadillo_bits/SpBase_bones.hpp
+++ b/include/armadillo_bits/SpBase_bones.hpp
@@ -100,9 +100,8 @@ struct SpBase
   inline arma_warn_unused bool has_inf()    const;
   inline arma_warn_unused bool has_nan()    const;
   
-  inline const SpOp<derived,spop_vectorise_col> as_col() const;
-  inline const SpOp<derived,spop_vectorise_row> as_row() const;
-  
+  inline arma_warn_unused const SpOp<derived,spop_vectorise_col> as_col() const;
+  inline arma_warn_unused const SpOp<derived,spop_vectorise_row> as_row() const;
   };
 
 
diff --git a/include/armadillo_bits/SpBase_meat.hpp b/include/armadillo_bits/SpBase_meat.hpp
index a8d7316e..6045c935 100644
--- a/include/armadillo_bits/SpBase_meat.hpp
+++ b/include/armadillo_bits/SpBase_meat.hpp
@@ -714,6 +714,7 @@ SpBase<elem_type,derived>::has_nan() const
 
 template<typename elem_type, typename derived>
 inline
+arma_warn_unused
 const SpOp<derived,spop_vectorise_col>
 SpBase<elem_type, derived>::as_col() const
   {
@@ -724,6 +725,7 @@ SpBase<elem_type, derived>::as_col() const
 
 template<typename elem_type, typename derived>
 inline
+arma_warn_unused
 const SpOp<derived,spop_vectorise_row>
 SpBase<elem_type, derived>::as_row() const
   {