diff --git a/src/CADShared/Runtime/Env.cs b/src/CADShared/Runtime/Env.cs
index 024eb5d45d3f3c49fa1583349ebfeaba8b5fdad8..888ee88c76dbeab938af7ba3f6b6cf5b63138f5f 100644
--- a/src/CADShared/Runtime/Env.cs
+++ b/src/CADShared/Runtime/Env.cs
@@ -289,7 +289,8 @@ public static ObjectId GetDimblkId(DimblkType dimblk)
         var oldDimblk = Acaop.GetSystemVariable("dimblk");
         Dimblk = dimblk;
         var id = HostApplicationServices.WorkingDatabase.Dimblk;
-        Acaop.SetSystemVariable("dimblk", oldDimblk);
+        if((string)oldDimblk!="") 
+            Acaop.SetSystemVariable("dimblk", oldDimblk);
         return id;
     }