diff --git a/migration/ram.c b/migration/ram.c
index 18ac68b181..521912385d 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -67,21 +67,25 @@
 /***********************************************************/
 /* ram save/restore */
 
-/* RAM_SAVE_FLAG_ZERO used to be named RAM_SAVE_FLAG_COMPRESS, it
- * worked for pages that where filled with the same char.  We switched
+/*
+ * RAM_SAVE_FLAG_ZERO used to be named RAM_SAVE_FLAG_COMPRESS, it
+ * worked for pages that were filled with the same char.  We switched
  * it to only search for the zero value.  And to avoid confusion with
- * RAM_SSAVE_FLAG_COMPRESS_PAGE just rename it.
+ * RAM_SAVE_FLAG_COMPRESS_PAGE just rename it.
  */
-
-#define RAM_SAVE_FLAG_FULL     0x01 /* Obsolete, not used anymore */
+/*
+ * RAM_SAVE_FLAG_FULL was obsoleted in 2009, it can be reused now
+ */
+#define RAM_SAVE_FLAG_FULL     0x01
 #define RAM_SAVE_FLAG_ZERO     0x02
 #define RAM_SAVE_FLAG_MEM_SIZE 0x04
 #define RAM_SAVE_FLAG_PAGE     0x08
 #define RAM_SAVE_FLAG_EOS      0x10
 #define RAM_SAVE_FLAG_CONTINUE 0x20
 #define RAM_SAVE_FLAG_XBZRLE   0x40
-/* 0x80 is reserved in migration.h start with 0x100 next */
+/* 0x80 is reserved in qemu-file.h for RAM_SAVE_FLAG_HOOK */
 #define RAM_SAVE_FLAG_COMPRESS_PAGE    0x100
+/* We can't use any flag that is bigger than 0x200 */
 
 int (*xbzrle_encode_buffer_func)(uint8_t *, uint8_t *, int,
      uint8_t *, int) = xbzrle_encode_buffer;