diff --git a/gtk/gtkcssprovider.c b/gtk/gtkcssprovider.c
index 9b05ee6493..f34cca3a0e 100644
--- a/gtk/gtkcssprovider.c
+++ b/gtk/gtkcssprovider.c
@@ -137,6 +137,7 @@ struct _GtkCssProviderPrivate
   GtkCssSelectorTree *tree;
   GResource *resource;
   char *path;
+  GBytes *bytes; /* *no* reference */
 };
 
 enum {
@@ -565,6 +566,16 @@ gtk_css_style_provider_lookup (GtkStyleProvider             *provider,
     *change = gtk_css_selector_tree_get_change_all (priv->tree, filter, node);
 }
 
+static gboolean
+gtk_css_style_provider_has_section (GtkStyleProvider *provider,
+                                    GtkCssSection    *section)
+{
+  GtkCssProvider *self = GTK_CSS_PROVIDER (provider);
+  GtkCssProviderPrivate *priv = gtk_css_provider_get_instance_private (self);
+
+  return priv->bytes == gtk_css_section_get_bytes (section);
+}
+
 static void
 gtk_css_style_provider_iface_init (GtkStyleProviderInterface *iface)
 {
@@ -572,6 +583,7 @@ gtk_css_style_provider_iface_init (GtkStyleProviderInterface *iface)
   iface->get_keyframes = gtk_css_style_provider_get_keyframes;
   iface->lookup = gtk_css_style_provider_lookup;
   iface->emit_error = gtk_css_style_provider_emit_error;
+  iface->has_section = gtk_css_style_provider_has_section;
 }
 
 static void
@@ -1157,6 +1169,7 @@ gtk_css_provider_load_internal (GtkCssProvider *self,
                                 GFile          *file,
                                 GBytes         *bytes)
 {
+  GtkCssProviderPrivate *priv = gtk_css_provider_get_instance_private (self);
   gint64 before G_GNUC_UNUSED;
 
   before = GDK_PROFILER_CURRENT_TIME;
@@ -1191,6 +1204,8 @@ gtk_css_provider_load_internal (GtkCssProvider *self,
         }
     }
 
+  priv->bytes = bytes;
+
   if (bytes)
     {
       GtkCssScanner *scanner;
diff --git a/gtk/gtkstyleprovider.c b/gtk/gtkstyleprovider.c
index d7c8af8687..a8098a3d60 100644
--- a/gtk/gtkstyleprovider.c
+++ b/gtk/gtkstyleprovider.c
@@ -170,6 +170,19 @@ gtk_style_provider_emit_error (GtkStyleProvider *provider,
     iface->emit_error (provider, section, error);
 }
 
+gboolean
+gtk_style_provider_has_section (GtkStyleProvider *provider,
+                                GtkCssSection    *section)
+{
+  GtkStyleProviderInterface *iface;
+
+  iface = GTK_STYLE_PROVIDER_GET_INTERFACE (provider);
+
+  if (iface->has_section)
+    return iface->has_section (provider, section);
+
+  return FALSE;
+}
 
 /* These apis are misnamed, and the rest of GtkStyleContext is deprecated,
  * so put them here for now
@@ -230,4 +243,3 @@ gtk_style_context_remove_provider_for_display (GdkDisplay       *display,
   cascade = _gtk_settings_get_style_cascade (gtk_settings_get_for_display (display), 1);
   _gtk_style_cascade_remove_provider (cascade, provider);
 }
-
diff --git a/gtk/gtkstyleproviderprivate.h b/gtk/gtkstyleproviderprivate.h
index 5319d57155..d2fca2c402 100644
--- a/gtk/gtkstyleproviderprivate.h
+++ b/gtk/gtkstyleproviderprivate.h
@@ -52,6 +52,8 @@ struct _GtkStyleProviderInterface
                                                  const GError            *error);
   /* signal */
   void                  (* changed)             (GtkStyleProvider        *provider);
+  gboolean              (* has_section)         (GtkStyleProvider        *provider,
+                                                 GtkCssSection           *section);
 };
 
 GtkSettings *           gtk_style_provider_get_settings          (GtkStyleProvider        *provider);
@@ -71,6 +73,8 @@ void                    gtk_style_provider_changed               (GtkStyleProvid
 void                    gtk_style_provider_emit_error            (GtkStyleProvider        *provider,
                                                                   GtkCssSection           *section,
                                                                   GError                  *error);
+gboolean                gtk_style_provider_has_section           (GtkStyleProvider        *provider,
+                                                                  GtkCssSection           *section);
 
 G_END_DECLS