diff --git a/glib/gmacros.h b/glib/gmacros.h
index d9c7906cd..1f4d779be 100644
--- a/glib/gmacros.h
+++ b/glib/gmacros.h
@@ -1101,9 +1101,11 @@
  * @struct_type: a structure type, e.g. #GOutputVector
  * @member: a field in the structure, e.g. `size`
  *
- * Returns: the size of @member in the struct definition without having a
+ * Returns the size of @member in the struct definition without having a
  * declared instance of @struct_type.
  *
+ * Returns: the size of @member in bytes.
+ *
  * Since: 2.64
  */
 #define G_SIZEOF_MEMBER(struct_type, member) \