Index: wp-admin/includes/schema.php
===================================================================
--- wp-admin/includes/schema.php	(revision 17041)
+++ wp-admin/includes/schema.php	(working copy)
@@ -327,6 +327,9 @@
 		$options[ 'permalink_structure' ] = '/%year%/%monthnum%/%day%/%postname%/';
 	}
 
+	// 3.1
+	'default_post_format' => 0,
+
 	// Set autoload to no for these options
 	$fat_options = array( 'moderation_keys', 'recently_edited', 'blacklist_keys' );
 
Index: wp-admin/includes/meta-boxes.php
===================================================================
--- wp-admin/includes/meta-boxes.php	(revision 17041)
+++ wp-admin/includes/meta-boxes.php	(working copy)
@@ -247,7 +247,7 @@
 	if ( is_array( $post_formats[0] ) ) :
 		$post_format = get_post_format( $post->ID );
 		if ( !$post_format )
-			$post_format = '0';
+			$post_format = get_option('default_post_format', '0');
 		$post_format_display = get_post_format_string( $post_format );
 		// Add in the current one if it isn't there yet, in case the current theme doesn't support it
 		if ( $post_format && !in_array( $post_format, $post_formats[0] ) )
Index: wp-admin/options.php
===================================================================
--- wp-admin/options.php	(revision 17041)
+++ wp-admin/options.php	(working copy)
@@ -60,7 +60,7 @@
 	'media' => array( 'thumbnail_size_w', 'thumbnail_size_h', 'thumbnail_crop', 'medium_size_w', 'medium_size_h', 'large_size_w', 'large_size_h', 'image_default_size', 'image_default_align', 'image_default_link_type', 'embed_autourls', 'embed_size_w', 'embed_size_h' ),
 	'privacy' => array( 'blog_public' ),
 	'reading' => array( 'posts_per_page', 'posts_per_rss', 'rss_use_excerpt', 'blog_charset', 'show_on_front', 'page_on_front', 'page_for_posts' ),
-	'writing' => array( 'default_post_edit_rows', 'use_smilies', 'default_category', 'default_email_category', 'use_balanceTags', 'default_link_category', 'enable_app', 'enable_xmlrpc' ),
+	'writing' => array( 'default_post_edit_rows', 'use_smilies', 'default_category', 'default_email_category', 'use_balanceTags', 'default_link_category', 'default_post_format', 'enable_app', 'enable_xmlrpc' ),
 	'options' => array( '' ) );
 
 $mail_options = array('mailserver_url', 'mailserver_port', 'mailserver_login', 'mailserver_pass');
Index: wp-admin/options-writing.php
===================================================================
--- wp-admin/options-writing.php	(revision 17041)
+++ wp-admin/options-writing.php	(working copy)
@@ -56,7 +56,24 @@
 ?>
 </td>
 </tr>
+<?php
+if ( current_theme_supports( 'post-formats' ) ) :
+	$post_formats = get_theme_support( 'post-formats' );
+	if ( is_array( $post_formats[0] ) ) :
+?>
 <tr valign="top">
+<th scope="row"><label for="default_post_format"><?php _e('Default Post Format') ?></label></th>
+<td>
+	<select name="default_post_format" id="default_post_format">
+		<option value="0"><?php _e('Standard'); ?></option>
+<?php foreach ( $post_formats[0] as $format ): ?>
+		<option<?php selected( get_option('default_post_format'), $format ); ?> value="<?php echo esc_attr( $format ); ?>"><?php echo esc_html( get_post_format_string( $format ) ); ?></option>
+<?php endforeach; ?>
+	</select></label>
+</td>
+</tr>
+<?php endif; endif; ?>
+<tr valign="top">
 <th scope="row"><label for="default_link_category"><?php _e('Default Link Category') ?></label></th>
 <td>
 <?php