diff --git a/docs/specs/qcow2.txt b/docs/specs/qcow2.txt
index 36a559d..e8bc189 100644
--- a/docs/specs/qcow2.txt
+++ b/docs/specs/qcow2.txt
@@ -80,7 +80,10 @@ in the description of a field.
                                 tables to repair refcounts before accessing the
                                 image.
 
-                    Bits 1-63:  Reserved (set to 0)
+                    Bit 1:      Deduplication bit.  If this bit is set then
+                                deduplication is used on this image.
+
+                    Bits 2-63:  Reserved (set to 0)
 
          80 -  87:  compatible_features
                     Bitmask of compatible features. An implementation can
@@ -116,6 +119,7 @@ be stored. Each extension has a structure like the following:
                         0x00000000 - End of the header extension area
                         0xE2792ACA - Backing file format name
                         0x6803f857 - Feature name table
+                        0xCD8E819B - Deduplication table offset and length
                         other      - Unknown header extension, can be safely
                                      ignored