diff --git a/rtdata/themes/RawTherapee.css b/rtdata/themes/RawTherapee.css
index cb1ba0591..508d21b38 100644
--- a/rtdata/themes/RawTherapee.css
+++ b/rtdata/themes/RawTherapee.css
@@ -51,7 +51,7 @@ GtkNotebook {
     padding: 4px 4px 4px 4px;
 }
 
-.filebrowser  GtkFrame {
+.filebrowserFrame {
      padding: 0px;
 }
 
diff --git a/rtgui/thumbbrowserbase.cc b/rtgui/thumbbrowserbase.cc
index 122973ac0..ea6969768 100644
--- a/rtgui/thumbbrowserbase.cc
+++ b/rtgui/thumbbrowserbase.cc
@@ -34,6 +34,7 @@ ThumbBrowserBase::ThumbBrowserBase ()
     Gtk::HBox* hb1 = Gtk::manage( new Gtk::HBox () );
     Gtk::HBox* hb2 = Gtk::manage( new Gtk::HBox () );
     Gtk::Frame* frame = Gtk::manage( new Gtk::Frame () );
+    frame->get_style_context()->add_class ("filebrowserFrame");
     frame->add (internal);
     frame->set_shadow_type (Gtk::SHADOW_IN );
     hb1->pack_start (*frame);