diff --git a/TestSuite/generics21.pas b/TestSuite/generics21.pas
new file mode 100644
index 000000000..7b7289e45
--- /dev/null
+++ b/TestSuite/generics21.pas
@@ -0,0 +1,40 @@
+type
+  t1<T>=class end;
+  t2=class(t1<byte>) end;
+  t3 = class(t2) end;
+  
+var i: integer;
+
+procedure p1<T>(self:t1<T>);
+begin
+  i := 1;
+end;
+procedure p2<T>(self:t1<T>); extensionmethod;
+begin
+  i := 2;
+end;
+procedure p3<T>(self:t1<T>); extensionmethod;
+begin
+  i := 2;
+end;
+procedure p3(self:t3); extensionmethod;
+begin
+  i := 3;
+end;
+begin
+  var a := new t2;
+  p1(a);
+  assert(i = 1);
+  a.p2;
+  assert(i = 2);
+  var b := new t3;
+  i := 0;
+  p1(b);
+  assert(i = 1);
+  b.p2;
+  assert(i = 2);
+  b.p3;
+  assert(i = 3);
+  a.p3;
+  assert(i = 2);
+end.
\ No newline at end of file
diff --git a/TreeConverter/TreeRealization/generics.cs b/TreeConverter/TreeRealization/generics.cs
index 92dbe3126..a2b210935 100644
--- a/TreeConverter/TreeRealization/generics.cs
+++ b/TreeConverter/TreeRealization/generics.cs
@@ -1183,9 +1183,19 @@ namespace PascalABCCompiler.TreeRealization
                 type_node fact_type_converted; //Сюда будет записан фактический тип или интерфейс, к которому он приводится
                 if (!fact_type.is_generic_type_instance || formal_type.original_generic != fact_type.original_generic)
                 {
-                    if (!formal_type.IsInterface) goto eq_cmp;
+                    //if (!formal_type.IsInterface) goto eq_cmp;
                     fact_type_converted = null;
-                    if (fact_type.ImplementingInterfaces != null)
+                    type_node base_type = fact_type.base_type;
+                    while (base_type != null)
+                    {
+                        if (base_type.original_generic == formal_type.original_generic)
+                        {
+                            fact_type_converted = base_type;
+                            break;
+                        }
+                        base_type = base_type.base_type;
+                    }
+                    if (fact_type.ImplementingInterfaces != null && fact_type_converted == null)
                     foreach (type_node ti in fact_type.ImplementingInterfaces)
                     {
                         if (ti.original_generic == formal_type.original_generic)