Index: src/wp-includes/ms-blogs.php
===================================================================
--- src/wp-includes/ms-blogs.php	(revision 30223)
+++ src/wp-includes/ms-blogs.php	(working copy)
@@ -296,8 +296,14 @@
 
 	$update_details = array();
 	$fields = array( 'site_id', 'domain', 'path', 'registered', 'last_updated', 'public', 'archived', 'mature', 'spam', 'deleted', 'lang_id');
-	foreach ( array_intersect( array_keys( $details ), $fields ) as $field )
-		$update_details[$field] = $details[$field];
+	foreach ( array_intersect( array_keys( $details ), $fields ) as $field ) {
+		if ( 'path' === $field ) {
+			$details[ $field ] = array_filter( explode( '/', $details[ $field ] ) );
+			$details[ $field ] = '/' . implode( '/', $details[ $field ] ) . '/';
+		}
+
+		$update_details[ $field ] = $details[ $field ];
+	}
 
 	$result = $wpdb->update( $wpdb->blogs, $update_details, array('blog_id' => $blog_id) );