diff --git a/gobject/gobject.c b/gobject/gobject.c
index 0eaba7e0e..c22b655d8 100644
--- a/gobject/gobject.c
+++ b/gobject/gobject.c
@@ -540,8 +540,10 @@ g_object_class_install_property (GObjectClass *class,
   g_return_if_fail (G_IS_PARAM_SPEC (pspec));
 
   if (CLASS_HAS_DERIVED_CLASS (class))
-    g_error ("Attempt to add property %s::%s to class after it was derived",
-	     G_OBJECT_CLASS_NAME (class), pspec->name);
+    g_error ("Attempt to add property %s::%s to class after it was derived", G_OBJECT_CLASS_NAME (class), pspec->name);
+
+  if (!g_type_is_in_init (G_OBJECT_CLASS_TYPE (class)))
+    g_critical ("Attempt to add property %s::%s after class was initialised", G_OBJECT_CLASS_NAME (class), pspec->name);
 
   class->flags |= CLASS_HAS_PROPS_FLAG;
 
@@ -653,6 +655,9 @@ g_object_class_install_properties (GObjectClass  *oclass,
     g_error ("Attempt to add properties to %s after it was derived",
              G_OBJECT_CLASS_NAME (oclass));
 
+  if (!g_type_is_in_init (G_OBJECT_CLASS_TYPE (oclass)))
+    g_critical ("Attempt to add properties %s after it was initialised", G_OBJECT_CLASS_NAME (oclass));
+
   oclass_type = G_OBJECT_CLASS_TYPE (oclass);
   parent_type = g_type_parent (oclass_type);
 
diff --git a/gobject/gtype-private.h b/gobject/gtype-private.h
index 5c415e5d0..d9e31e482 100644
--- a/gobject/gtype-private.h
+++ b/gobject/gtype-private.h
@@ -72,6 +72,7 @@ void        _g_closure_invoke_va (GClosure       *closure,
 				  int             n_params,
 				  GType          *param_types);
 
+gboolean    g_type_is_in_init    (GType type);
 
 G_END_DECLS
 
diff --git a/gobject/gtype.c b/gobject/gtype.c
index 01a00dc6e..8d5df09d0 100644
--- a/gobject/gtype.c
+++ b/gobject/gtype.c
@@ -4701,3 +4701,13 @@ g_type_ensure (GType type)
   if (G_UNLIKELY (type == (GType)-1))
     g_error ("can't happen");
 }
+
+gboolean
+g_type_is_in_init (GType type)
+{
+  TypeNode *node;
+
+  node = lookup_type_node_I (type);
+
+  return node->data->class.init_state != INITIALIZED;
+}