diff --git a/TestSuite/where16.pas b/TestSuite/where16.pas
index 229097938..d30f42aba 100644
--- a/TestSuite/where16.pas
+++ b/TestSuite/where16.pas
@@ -1,18 +1,20 @@
 type
   
-  c1<T1> = class where T1: c1<T1>;
+  c1<T1> = class
+  where T1: c1<T1>;
     
   end;
   
   //Ошибка: Несоответствие спецификатора whеre спецификатору where базового класса
-  c2<T2> = class(c1<T2>) where T2: c1<T2>;
+  c2<T2> = class(c1<T2>)
+  where T2: c1<T2>;
     
   end;
   
   c3 = class(c1<c3>)
   end;
   
-begin 
-new c2<c3>;
-new c3;
+begin
+  new c2<c3>;
+  new c3;
 end.
\ No newline at end of file
diff --git a/TestSuite/where18.pas b/TestSuite/where18.pas
new file mode 100644
index 000000000..4094c9975
--- /dev/null
+++ b/TestSuite/where18.pas
@@ -0,0 +1,16 @@
+// #2519
+type
+  Base = class end;
+  Def = class(Base) end;
+  
+  t0<T> = class
+  where T: Base;
+    
+  end;
+  //Ошибка: Несоответствие спецификатора where спецификатору where базового класса
+  t1<T2> = class(t0<T2>)
+  where T2: Def;
+    
+  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 39bd9c1ba..bc8869190 100644
--- a/TreeConverter/TreeConversion/syntax_tree_visitor.cs
+++ b/TreeConverter/TreeConversion/syntax_tree_visitor.cs
@@ -12762,7 +12762,13 @@ namespace PascalABCCompiler.TreeConverter
                                 AddError(ctn.loc, "WHERE_SPECIFIER_MISMATCH");
                             if (t.methods.Length > thist.methods.Length)
                                 AddError(ctn.loc, "WHERE_SPECIFIER_MISMATCH");
-                            if (t.base_type != SystemLibrary.SystemLibrary.object_type && !type_table.is_type_or_original_generics_equal(t.base_type as type_node, thist.base_type as type_node))
+
+                            var old_base = t.base_type as type_node;
+                            var new_base = thist.base_type as type_node;
+                            //ToDo: (тест where16) с1<T1> и c1<T2> это не всегда одно и тоже - только если T2 подставили вместо T1
+                            old_base = old_base.original_generic;
+                            new_base = new_base.original_generic;
+                            if (old_base!=new_base && !type_table.is_derived(old_base, new_base))
                                 AddError(ctn.loc, "WHERE_SPECIFIER_MISMATCH");
                                 
                         }