diff --git a/vapi/gtksourceview-2.0.vapi b/vapi/gtksourceview-2.0.vapi
index 98dcf26..7d09e55 100644
--- a/vapi/gtksourceview-2.0.vapi
+++ b/vapi/gtksourceview-2.0.vapi
@@ -66,7 +66,7 @@ namespace Gtk {
 		public unowned string[]? get_language_ids ();
 		[CCode (array_length = false, array_null_terminated = true)]
 		public unowned string[]? get_search_path ();
-		public unowned Gtk.SourceLanguage guess_language (string filename, string content_type);
+		public unowned Gtk.SourceLanguage guess_language (string? filename, string? content_type);
 		public void set_search_path ([CCode (array_length = false)] string[]? dirs);
 		[CCode (array_length = false, array_null_terminated = true)]
 		public string[] language_ids { get; }
diff --git a/vapi/packages/gtksourceview-2.0/gtksourceview-2.0.metadata b/vapi/packages/gtksourceview-2.0/gtksourceview-2.0.metadata
index 1956e1e..8783c93 100644
--- a/vapi/packages/gtksourceview-2.0/gtksourceview-2.0.metadata
+++ b/vapi/packages/gtksourceview-2.0/gtksourceview-2.0.metadata
@@ -14,6 +14,8 @@ GtkSourceContextEngine hidden="1"
 GtkSourceContextReplace hidden="1"
 GtkSourceEngine hidden="1"
 GtkSourceLanguageManager cheader_filename="gtksourceview/gtksourcelanguagemanager.h"
+gtk_source_language_manager_guess_language.filename nullable="1"
+gtk_source_language_manager_guess_language.content_type nullable="1"
 gtk_source_language_manager_get_language_ids is_array="1" nullable="1" array_null_terminated="1"
 gtk_source_language_manager_get_search_path is_array="1" nullable="1" array_null_terminated="1"
 gtk_source_language_manager_set_search_path.dirs is_array="1" nullable="1" array_null_terminated="1"
