diff --git a/glib/gmem.c b/glib/gmem.c
index d7076193b..44e128020 100644
--- a/glib/gmem.c
+++ b/glib/gmem.c
@@ -145,7 +145,7 @@ g_malloc0 (gsize n_bytes)
 
 /**
  * g_realloc:
- * @mem: the memory to reallocate
+ * @mem: (allow-none): the memory to reallocate
  * @n_bytes: new size of the memory in bytes
  * 
  * Reallocates the memory pointed to by @mem, so that it now has space for
@@ -183,7 +183,7 @@ g_realloc (gpointer mem,
 
 /**
  * g_free:
- * @mem: the memory to free
+ * @mem: (allow-none): the memory to free
  * 
  * Frees the memory pointed to by @mem.
  * If @mem is %NULL it simply returns.
@@ -369,7 +369,7 @@ g_malloc0_n (gsize n_blocks,
 
 /**
  * g_realloc_n:
- * @mem: the memory to reallocate
+ * @mem: (allow-none): the memory to reallocate
  * @n_blocks: the number of blocks to allocate
  * @n_block_bytes: the size of each block in bytes
  *