diff --git a/objects/line_imp.h b/objects/line_imp.h
--- a/objects/line_imp.h
+++ b/objects/line_imp.h
@@ -113,6 +113,7 @@
   ObjectImp* property( int which, const KigDocument& d ) const Q_DECL_OVERRIDE;
   const char* iconForProperty( int which ) const Q_DECL_OVERRIDE;
   const ObjectImpType* impRequirementForProperty( int which ) const Q_DECL_OVERRIDE;
+  bool isPropertyDefinedOnOrThroughThisImp( int which ) const Q_DECL_OVERRIDE;
 
   SegmentImp* copy() const Q_DECL_OVERRIDE;
 
@@ -168,6 +169,7 @@
   ObjectImp* property( int which, const KigDocument& d ) const Q_DECL_OVERRIDE;
   const char* iconForProperty( int which ) const Q_DECL_OVERRIDE;
   const ObjectImpType* impRequirementForProperty( int which ) const Q_DECL_OVERRIDE;
+  bool isPropertyDefinedOnOrThroughThisImp( int which ) const Q_DECL_OVERRIDE;
 
   RayImp* copy() const Q_DECL_OVERRIDE;
 
diff --git a/objects/line_imp.cc b/objects/line_imp.cc
--- a/objects/line_imp.cc
+++ b/objects/line_imp.cc
@@ -633,12 +633,44 @@
     return Parent::isPropertyDefinedOnOrThroughThisImp( which );
   else if ( which == Parent::numberOfProperties() + pnum++ )
     return false;
+  else if ( which == Parent::numberOfProperties() + pnum++ )
+    return false;
+  else assert( false );
+  return false;
+}
+
+bool SegmentImp::isPropertyDefinedOnOrThroughThisImp( int which ) const
+{
+  int pnum = 0;
+
+  if ( which < Parent::numberOfProperties() )
+    return Parent::isPropertyDefinedOnOrThroughThisImp( which );
+  else if ( which == Parent::numberOfProperties() + pnum++ )
+    return false;
+  else if ( which == Parent::numberOfProperties() + pnum++ )
+    return true;
   else if ( which == Parent::numberOfProperties() + pnum++ )
     return true;
   else if ( which == Parent::numberOfProperties() + pnum++ )
     return true;
   else if ( which == Parent::numberOfProperties() + pnum++ )
     return true;
+  else if ( which == Parent::numberOfProperties() + pnum++ )
+    return true;
+  else assert( false );
+  return false;
+}
+
+bool RayImp::isPropertyDefinedOnOrThroughThisImp( int which ) const
+{
+  int pnum = 0;
+
+  if ( which < Parent::numberOfProperties() )
+    return Parent::isPropertyDefinedOnOrThroughThisImp( which );
+  else if ( which == Parent::numberOfProperties() + pnum++ )
+    return true;
+  else if ( which == Parent::numberOfProperties() + pnum++ )
+    return true;
   else assert( false );
   return false;
 }