diff --git a/gio/gvdb/gvdb-reader.c b/gio/gvdb/gvdb-reader.c
index ccae40e64..83ad2ac19 100644
--- a/gio/gvdb/gvdb-reader.c
+++ b/gio/gvdb/gvdb-reader.c
@@ -332,7 +332,7 @@ gvdb_table_list_from_item (GvdbTable                    *table,
 /**
  * gvdb_table_get_names:
  * @table: a #GvdbTable
- * @length: (optional): the number of items returned, or %NULL
+ * @length: (out) (optional): the number of items returned, or %NULL
  *
  * Gets a list of all names contained in @table.
  *
diff --git a/glib/gtree.c b/glib/gtree.c
index 115f44659..e8d4e204c 100644
--- a/glib/gtree.c
+++ b/glib/gtree.c
@@ -853,8 +853,8 @@ g_tree_lookup (GTree         *tree,
  * g_tree_lookup_extended:
  * @tree: a #GTree
  * @lookup_key: the key to look up
- * @orig_key: (optional) (nullable): returns the original key
- * @value: (optional) (nullable): returns the value associated with the key
+ * @orig_key: (out) (optional) (nullable): returns the original key
+ * @value: (out) (optional) (nullable): returns the value associated with the key
  * 
  * Looks up a key in the #GTree, returning the original key and the
  * associated value. This is useful if you need to free the memory
diff --git a/glib/gvarianttypeinfo.c b/glib/gvarianttypeinfo.c
index bed0bb717..2904686b8 100644
--- a/glib/gvarianttypeinfo.c
+++ b/glib/gvarianttypeinfo.c
@@ -223,8 +223,8 @@ g_variant_type_info_get_type_string (GVariantTypeInfo *info)
 /* < private >
  * g_variant_type_info_query:
  * @info: a #GVariantTypeInfo
- * @alignment: (optional): the location to store the alignment, or %NULL
- * @fixed_size: (optional): the location to store the fixed size, or %NULL
+ * @alignment: (out) (optional): the location to store the alignment, or %NULL
+ * @fixed_size: (out) (optional): the location to store the fixed size, or %NULL
  *
  * Queries @info to determine the alignment requirements and fixed size
  * (if any) of the type.
@@ -332,8 +332,8 @@ g_variant_type_info_element (GVariantTypeInfo *info)
 /* < private >
  * g_variant_type_query_element:
  * @info: a #GVariantTypeInfo for an array or maybe type
- * @alignment: (optional): the location to store the alignment, or %NULL
- * @fixed_size: (optional): the location to store the fixed size, or %NULL
+ * @alignment: (out) (optional): the location to store the alignment, or %NULL
+ * @fixed_size: (out) (optional): the location to store the fixed size, or %NULL
  *
  * Returns the alignment requires and fixed size (if any) for the
  * element type of the array.  This call is a convenience wrapper around