diff --git a/src/Widgets/FormatBar.vala b/src/Widgets/FormatBar.vala
index 3616d59246..0cfee4d666 100644
--- a/src/Widgets/FormatBar.vala
+++ b/src/Widgets/FormatBar.vala
@@ -270,16 +270,21 @@ public class Code.FormatBar : Gtk.Box {
         goto_entry.text = "%d.%d".printf (line, iter.get_line_offset () + 1);
     }
 
-    public void set_document (Scratch.Services.Document doc) {
-        if (this.doc != null) {
-            this.doc.source_view.buffer.notify["cursor-position"].disconnect (format_line_header);
+    public void set_document (Scratch.Services.Document set_doc) requires (set_doc != null) {
+         if (doc != null) {
+            doc.source_view.notify["language"].disconnect (update_current_lang);
+            doc.source_view.buffer.notify["cursor-position"].disconnect (format_line_header);
         }
 
-        this.doc = doc;
+        doc = set_doc;
+
+        doc.source_view.notify["language"].connect (update_current_lang);
         update_current_lang ();
-        format_tab_header_from_global_settings ();
+
+        doc.source_view.buffer.notify["cursor-position"].connect (format_line_header);
         format_line_header ();
-        this.doc.source_view.buffer.notify["cursor-position"].connect (format_line_header);
+
+        format_tab_header_from_global_settings ();
     }
 
     public void set_insert_spaces_instead_of_tabs (bool use_spaces) {