diff --git a/property/generic_property.hpp b/property/generic_property.hpp
index 4c2b3d1..08e91c5 100644
--- a/property/generic_property.hpp
+++ b/property/generic_property.hpp
@@ -399,6 +399,39 @@ namespace motor
                 return _is ;
             }
 
+            void_t replace_is( motor::wire::iinput_slot_mtr_safe_t s, bool_t const take_old_value ) noexcept
+            {
+                if ( s.mtr() == _is ) 
+                {
+                    motor::release( motor::move( s ) ) ;
+                    return ;
+                }
+
+                auto * s_ = dynamic_cast<typename this_t::is_mtr_t>( s.mtr() ) ;
+                if ( s_ == nullptr )
+                {
+                    motor::release( motor::move( s ) ) ;
+                    return ;
+                }
+
+                if( take_old_value && _is != nullptr )
+                    s_->set_value( _is->get_value() ) ;
+                    
+                motor::release( motor::move( _is ) ) ;
+                _is = s_ ;
+            }
+
+            void_t replace_is( motor::wire::iinput_slot_mtr_safe_t s ) noexcept
+            {
+                this_t::replace_is( motor::move( s ), false ) ;
+            }
+
+            void_t replace_is( typename this_t::is_mtr_safe_t s ) noexcept
+            {
+                motor::release( motor::move( _is ) ) ;
+                _is = motor::move( s ) ;
+            }
+
         public:
 
             static bool_t create_property( motor::wire::iinput_slot_mtr_t is, this_t & prop_out ) noexcept
diff --git a/property/property_sheet.hpp b/property/property_sheet.hpp
index 8cb674a..af55107 100644
--- a/property/property_sheet.hpp
+++ b/property/property_sheet.hpp
@@ -154,14 +154,15 @@ namespace motor
         template< typename T >
         static bool_t add_is_property( motor::string_in_t name, motor::wire::iinput_slot_ptr_t is, motor::property::property_sheet_inout_t props )
         {
-            using property_t = motor::property::generic_property<motor::wire::input_slot< T > > ;
+            using type_t = motor::wire::input_slot< T > ;
+            using property_t = motor::property::generic_property< type_t > ;
             property_t p ;
 
             if ( property_t::create_property( is, p ) )
             {
                 if( !props.add_property( name, std::move( p ) ) )
                 {
-                    return props.borrow_property< T >( name ) != nullptr ;
+                    return props.borrow_property< type_t >( name ) != nullptr ;
                 }
                 return true ;
             }