--- p/objects.c.orig	Wed Aug  2 14:19:58 2006
+++ p/objects.c	Wed Aug  2 14:21:29 2006
@@ -797,8 +797,9 @@
 
   if (TYPE_LANG_CODE (type) == PASCAL_LANG_ABSTRACT_OBJECT)
     {
-      /* Set `Size' and `NegatedSize' to 0 for abstract objects */
-      TREE_VALUE (vmt_entry) = TREE_VALUE (TREE_CHAIN (vmt_entry)) = size_zero_node;
+      /* Set `Size' to 0 and `NegatedSize' to -1 for abstract objects */
+      TREE_VALUE (vmt_entry) = size_zero_node;
+      TREE_VALUE (TREE_CHAIN (vmt_entry)) = size_int (-1);
       if (co->warn_inherited_abstract && parent && TYPE_LANG_CODE (parent) != PASCAL_LANG_ABSTRACT_OBJECT)
         warning ("abstract object type `%s' inherits from non-abstract type `%s'",
                  object_name, IDENTIFIER_NAME (DECL_NAME (TYPE_NAME (parent))));
--- p/doc/en/reference.texi.orig	Wed Aug  2 14:22:41 2006
+++ p/doc/en/reference.texi	Wed Aug  2 14:24:01 2006
@@ -9298,10 +9298,14 @@
 object type and can be accessed via @samp{TypeOf}.
 
 @samp{Size} contains the size of the object type, @samp{NegatedSize}
-contains the size negated (for runtime checks). @samp{Parent}
-contains a pointer to the parent type's VMT (or nil if the type has
-no parent). @samp{Name} points to a string containing the type's
-name.
+contains the size negated (for optional runtime checks).
+@samp{Parent} contains a pointer to the parent type's VMT (or nil if
+the type has no parent). @samp{Name} points to a string containing
+the type's name.
+
+For abstract object types, @samp{Size} contains 0 and
+@samp{NegatedSize} contains -1, so they will always fail the runtime
+check.
 
 @subheading Conforming to
 
--- p/test/fjf1105.pas.orig	Wed Aug  2 14:28:08 2006
+++ p/test/fjf1105.pas	Wed Aug  2 14:24:19 2006
@@ -0,0 +1,47 @@
+{$object-checking}
+
+program fjf1105 (Output);
+
+uses GPC;
+
+type
+  px = ^tx;
+  tx = abstract object
+    procedure p; abstract;
+  end;
+
+  py = ^ty;
+  ty = object (tx)
+    constructor c;
+    procedure p; virtual;
+  end;
+
+constructor ty.c;
+begin
+end;
+
+procedure ty.p;
+begin
+  WriteLn ('ty.p')
+end;
+
+procedure ExpectError;
+begin
+  if ExitCode = 0 then
+    WriteLn ('failed')
+  else
+    begin
+      WriteLn ('OK');
+      Halt (0) {!}
+    end
+end;
+
+var
+  a: px;
+
+begin
+  AtExit (ExpectError);
+  a := New (py);
+  SetType (a^, TypeOf (a^)^.Parent);
+  a^.p
+end.