--- revision.php	Wed Jun 20 15:44:22 2012
+++ revision-patched.php	Thu Jul  5 10:06:16 2012
@@ -169,14 +169,17 @@
 $identical = true;
 foreach ( _wp_post_revision_fields() as $field => $field_title ) :
 	if ( 'diff' == $action ) {
-		$left_content = apply_filters( "_wp_post_revision_field_$field", $left_revision->$field, $field );
-		$right_content = apply_filters( "_wp_post_revision_field_$field", $right_revision->$field, $field );
+		$left_value = isset($left_revision->$field) ? $left_revision->$field : get_metadata( 'post', $left_revision->ID, $field, true );
+		$left_content = apply_filters( "_wp_post_revision_field_$field", $left_value, $field );
+		$right_value = isset($right_revision->$field) ? $right_revision->$field : get_metadata( 'post', $right_revision->ID, $field, true );
+		$right_content = apply_filters( "_wp_post_revision_field_$field", $right_value, $field );
 		if ( !$content = wp_text_diff( $left_content, $right_content ) )
 			continue; // There is no difference between left and right
 		$identical = false;
 	} else {
 		add_filter( "_wp_post_revision_field_$field", 'htmlspecialchars' );
-		$content = apply_filters( "_wp_post_revision_field_$field", $revision->$field, $field );
+		$value = isset($revision->$field) ? $revision->$field : get_metadata( 'post', $revision->ID, $field, true );
+		$content = apply_filters( "_wp_post_revision_field_$field", $value, $field );
 	}
 	?>