diff --git a/TestSuite/where11.pas b/TestSuite/where11.pas
new file mode 100644
index 000000000..d6bdd6df4
--- /dev/null
+++ b/TestSuite/where11.pas
@@ -0,0 +1,14 @@
+type
+  
+  t1<T> = class where T: t1<T>;
+    
+    function p1: T;
+    begin
+      var a: t1<T>;
+      var b := a as T;
+    end;
+    
+  end;
+  
+begin 
+end.
\ No newline at end of file
diff --git a/TreeConverter/TreeConversion/syntax_tree_visitor.cs b/TreeConverter/TreeConversion/syntax_tree_visitor.cs
index 5ea7fff54..501adcd49 100644
--- a/TreeConverter/TreeConversion/syntax_tree_visitor.cs
+++ b/TreeConverter/TreeConversion/syntax_tree_visitor.cs
@@ -3085,7 +3085,7 @@ namespace PascalABCCompiler.TreeConverter
             }
             else
             {
-                if (tp.is_generic_parameter && !tp.is_class && !(tp.base_type != null && tp.base_type.is_class))
+                if (tp.is_generic_parameter && !tp.is_class && !(tp.base_type != null && tp.base_type.is_class) && !(tp.base_type != null && tp.base_type.original_generic != null && tp.base_type.original_generic.is_class))
                     AddError(get_location(node.type_def), "OPERATOR_AS_CAN_NOT_BE_USED_WITH_GENERIC_PARAMETER_{0}_WITHOUT_CLASS_CONSTRAINT", tp.name);
                 if (tp.is_value_type)
                     AddError(get_location(node.type_def), "OPERATOR_AS_MUST_BE_USED_WITCH_A_REFERENCE_TYPE_VALUETYPE{0}", tp.PrintableName);