diff --git a/app/core/gimpgrouplayer.c b/app/core/gimpgrouplayer.c
index ce1f6d2e22..eee85fb8bc 100644
--- a/app/core/gimpgrouplayer.c
+++ b/app/core/gimpgrouplayer.c
@@ -74,7 +74,8 @@ struct _GimpGroupLayerPrivate
   gboolean        reallocate_projection;
 };
 
-#define GET_PRIVATE(item) ((GimpGroupLayerPrivate *) gimp_group_layer_get_instance_private ((GimpGroupLayer *) (item)))
+#define GET_PRIVATE(item) \
+  ((GimpGroupLayerPrivate *) gimp_group_layer_get_instance_private ((GimpGroupLayer *) (item)))
 
 
 static void            gimp_projectable_iface_init   (GimpProjectableInterface  *iface);
diff --git a/app/core/gimpgrouplayer.h b/app/core/gimpgrouplayer.h
index 7783156f13..c04d73ddff 100644
--- a/app/core/gimpgrouplayer.h
+++ b/app/core/gimpgrouplayer.h
@@ -23,21 +23,13 @@
 #include "gimplayer.h"
 
 
-#define GIMP_TYPE_GROUP_LAYER            (gimp_group_layer_get_type ())
-#define GIMP_GROUP_LAYER(obj)            (G_TYPE_CHECK_INSTANCE_CAST ((obj), GIMP_TYPE_GROUP_LAYER, GimpGroupLayer))
-#define GIMP_GROUP_LAYER_CLASS(klass)    (G_TYPE_CHECK_CLASS_CAST ((klass), GIMP_TYPE_GROUP_LAYER, GimpGroupLayerClass))
-#define GIMP_IS_GROUP_LAYER(obj)         (G_TYPE_CHECK_INSTANCE_TYPE ((obj), GIMP_TYPE_GROUP_LAYER))
-#define GIMP_IS_GROUP_LAYER_CLASS(klass) (G_TYPE_CHECK_CLASS_TYPE ((klass), GIMP_TYPE_GROUP_LAYER))
-#define GIMP_GROUP_LAYER_GET_CLASS(obj)  (G_TYPE_INSTANCE_GET_CLASS ((obj), GIMP_TYPE_GROUP_LAYER, GimpGroupLayerClass))
+#define GIMP_TYPE_GROUP_LAYER (gimp_group_layer_get_type ())
+G_DECLARE_DERIVABLE_TYPE (GimpGroupLayer,
+                          gimp_group_layer,
+                          GIMP, GROUP_LAYER,
+                          GimpLayer)
 
 
-typedef struct _GimpGroupLayerClass GimpGroupLayerClass;
-
-struct _GimpGroupLayer
-{
-  GimpLayer  parent_instance;
-};
-
 struct _GimpGroupLayerClass
 {
   GimpLayerClass  parent_class;
diff --git a/app/core/gimplayer.h b/app/core/gimplayer.h
index 6748ebc879..f02d6038bf 100644
--- a/app/core/gimplayer.h
+++ b/app/core/gimplayer.h
@@ -246,3 +246,5 @@ gboolean        gimp_layer_is_alpha_locked     (GimpLayer            *layer,
 
 void          gimp_layer_update_effective_mode (GimpLayer            *layer);
 void       gimp_layer_update_excludes_backdrop (GimpLayer            *layer);
+
+G_DEFINE_AUTOPTR_CLEANUP_FUNC (GimpLayer, g_object_unref);