diff --git a/.gitattributes b/.gitattributes
index 2de6c0760f..40b939d1a8 100644
--- a/.gitattributes
+++ b/.gitattributes
@@ -11334,6 +11334,7 @@ tests/webtbf/tw20907.pp svneol=native#text/plain
 tests/webtbf/tw20907a.pp svneol=native#text/plain
 tests/webtbf/tw21078.pp svneol=native#text/plain
 tests/webtbf/tw21087.pp svneol=native#text/plain
+tests/webtbf/tw21238.pp svneol=native#text/pascal
 tests/webtbf/tw2128.pp svneol=native#text/plain
 tests/webtbf/tw2129.pp svneol=native#text/plain
 tests/webtbf/tw21466.pas svneol=native#text/pascal
diff --git a/compiler/ptype.pas b/compiler/ptype.pas
index 5df541e436..eb662085f4 100644
--- a/compiler/ptype.pas
+++ b/compiler/ptype.pas
@@ -922,7 +922,8 @@ implementation
                      begin
                        generate_specialization(def,false,name,nil,'');
                        { handle nested types }
-                       post_comp_expr_gendef(def);
+                       if assigned(def) then
+                         post_comp_expr_gendef(def);
                      end
                    else
                      begin
diff --git a/tests/webtbf/tw21238.pp b/tests/webtbf/tw21238.pp
new file mode 100644
index 0000000000..176035655d
--- /dev/null
+++ b/tests/webtbf/tw21238.pp
@@ -0,0 +1,12 @@
+{ %fail }
+{$mode delphi}
+uses
+  classes;
+procedure FormShow(Sender: TObject);
+var
+  List: TList<Byte>;
+begin
+end;
+
+begin
+end.