diff --git a/src/GEOMImpl/GEOMImpl_BlockDriver.cxx b/src/GEOMImpl/GEOMImpl_BlockDriver.cxx
index f13daca80..95c2dbf08 100644
--- a/src/GEOMImpl/GEOMImpl_BlockDriver.cxx
+++ b/src/GEOMImpl/GEOMImpl_BlockDriver.cxx
@@ -18,7 +18,6 @@
 // Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
 //
 // See http://www.salome-platform.org/ or email : webmaster.salome@opencascade.com
-//
 
 #include <Standard_Stream.hxx>
 
@@ -562,6 +561,12 @@ Standard_Integer GEOMImpl_BlockDriver::Execute(TFunction_Logbook& log) const
         Standard_NullObject::Raise("Null Shape given");
       }
 
+      // Copy shape to avoid problems (Mantis issue 0021683)
+      TopoDS_Shape aShapeCopy;
+      TColStd_IndexedDataMapOfTransientTransient aMapTShapes;
+      TNaming_CopyShape::CopyTool(aBlockOrComp, aMapTShapes, aShapeCopy);
+      aBlockOrComp = aShapeCopy;
+
       // 1. Improve solids with seam and/or degenerated edges
       BlockFix_BlockFixAPI aTool;
       //aTool.Tolerance() = toler;