Ticket #28573: 28573-3.diff

functions.php

@@ -385 +385 @@
  *
  * Adds body classes to denote:
  * 1. Single or multiple authors.
- * 2. Presence of header image.
+ * 2. Presence of header image except in Multisite signup and activate pages.
  * 3. Index views.
  * 4. Full-width content layout.
  * 5. Presence of footer widgets.
@@ -404 +404 @@
 
         if ( get_header_image() ) {
                 $classes[] = 'header-image';
-        } else {
-                $classes[] = 'masthead-fixed';
+        } elseif ( ! in_array( $GLOBALS['pagenow'], array( 'wp-activate.php', 'wp-signup.php' ) ) ) { 
+                $classes[] = 'masthead-fixed';  
         }
 
         if ( is_archive() || is_search() || is_home() ) {