diff --git a/TestSuite/nil1.pas b/TestSuite/nil1.pas
index a614a774c..a221bbc9f 100644
--- a/TestSuite/nil1.pas
+++ b/TestSuite/nil1.pas
@@ -1,4 +1,4 @@
-
+
 type TRec = record
 a : object;
 arr : array of object;
@@ -17,5 +17,6 @@ var v : object := nil;
     rec2 : TRec:=(a:nil;arr:(nil,nil));
     
 begin
-
+  assert(arr4[2] = nil);
+  assert(rec2.a = nil);
 end.
\ No newline at end of file
diff --git a/TestSuite/nil2.pas b/TestSuite/nil2.pas
new file mode 100644
index 000000000..81453f531
--- /dev/null
+++ b/TestSuite/nil2.pas
@@ -0,0 +1,12 @@
+begin
+  var s1 := Seq('abc','def');
+  var s2 := s1 + string(nil); //Вызывает это: function operator+<T>(a, b: sequence of T): sequence of T; extensionmethod;
+  assert(s2.ToArray[2] = nil);
+  var i := 0;
+  try
+    var s3 := s1 + nil;
+  except
+    i := 1;
+  end;
+  assert(i = 1);
+end.
\ No newline at end of file
diff --git a/TreeConverter/TreeConversion/convertion_data_and_alghoritms.cs b/TreeConverter/TreeConversion/convertion_data_and_alghoritms.cs
index 61b7e171f..c644dd337 100644
--- a/TreeConverter/TreeConversion/convertion_data_and_alghoritms.cs
+++ b/TreeConverter/TreeConversion/convertion_data_and_alghoritms.cs
@@ -669,7 +669,8 @@ namespace PascalABCCompiler.TreeConverter
             {
                 return from;
             }
-
+            
+            
             possible_type_convertions ptc = type_table.get_convertions(from.type, to, false);
             if (ptc.second != null)
             {
@@ -687,7 +688,7 @@ namespace PascalABCCompiler.TreeConverter
                     ret.conversion_type = conv_type;
                 return ret;
             }
-
+            
             if ((type_table.is_derived(from.type, to)) || (type_table.is_derived(to, from.type)) || from.type.IsInterface || to.IsInterface && !(from.type is delegated_methods))
             {
                 if (from.type.IsSealed && to.IsInterface && !from.type.ImplementingInterfaces.Contains(to) ||
diff --git a/TreeConverter/TreeConversion/syntax_tree_visitor.cs b/TreeConverter/TreeConversion/syntax_tree_visitor.cs
index b1a81c4e6..2e0872567 100644
--- a/TreeConverter/TreeConversion/syntax_tree_visitor.cs
+++ b/TreeConverter/TreeConversion/syntax_tree_visitor.cs
@@ -1087,7 +1087,8 @@ namespace PascalABCCompiler.TreeConverter
             {
             	if ( !type_table.is_with_nil_allowed(left.type) && !left.type.IsPointer)
                     AddError(right.location, "NIL_WITH_VALUE_TYPES_NOT_ALLOWED");
-            	right = null_const_node.get_const_node_with_type(left.type, (null_const_node)right);
+                if (right.conversion_type == null)
+                    right = null_const_node.get_const_node_with_type(left.type, (null_const_node)right);
             }
 
             /*if (left.semantic_node_type == semantic_node_type.null_const_node)