diff --git a/bin/glance b/bin/glance
index b4857b60ba..5bbc22d038 100755
--- a/bin/glance
+++ b/bin/glance
@@ -173,10 +173,14 @@ is_public           Optional. If specified, interpreted as a boolean value
 protected           Optional. If specified, interpreted as a boolean value
                     and enables or disables deletion protection.
                     The default value is False.
-disk_format         Required. Possible values are 'ami','ari','aki', 'vhd',
-                    'vmk', 'raw', 'qcow2' and 'vdi'.
-container_format    Required. Possible values are 'ami', 'ari', 'aki' 'bare'
-                    and 'ovf'.
+disk_format         Required. If unspecified and container_format is specified
+                    as 'ami', 'ari' or 'aki', disk_format will default to the
+                    container_format value. Possible values are 'ami', 'ari',
+                    'aki', 'vhd', 'vmk', 'raw', 'qcow2' and 'vdi'.
+container_format    Required. If unspecified and disk_format is specified as
+                    'ami', 'ari' or 'aki', container_format will default to the
+                    disk_format value. Possible values are 'ami', 'ari', 'aki',
+                    'bare' and 'ovf'.
 location            Optional. When specified, should be a readable location
                     in the form of a URI: $STORE://LOCATION. For example, if
                     the image data is stored in a file on the local
diff --git a/doc/source/glance.rst b/doc/source/glance.rst
index 2f118a5dab..cf5b8cf049 100644
--- a/doc/source/glance.rst
+++ b/doc/source/glance.rst
@@ -229,7 +229,9 @@ Here is how we'd upload this image to Glance::
        container_format=bare disk_format=qcow2 < /tmp/images/myimage.img
 
 Note that the disk container formats are no longer defaulted and are thus
-strictly required.
+strictly required. However, if only one of disk or container format is specified
+and is in Amazon format, the other parameter defaults to the specified
+disk or container format value.
 
 If Glance was able to successfully upload and store your VM image data and
 metadata attributes, you would see something like this::