Index: src/wp-includes/class-wp-site-query.php
===================================================================
--- src/wp-includes/class-wp-site-query.php	(revision 37899)
+++ src/wp-includes/class-wp-site-query.php	(working copy)
@@ -264,16 +264,18 @@
 
 			$cache_value = array(
 				'site_ids' => $site_ids,
-				'found_sites' => $this->found_sites,
-				'max_num_pages' => $this->max_num_pages,
+				'found_sites' => $this->found_sites
 			);
 			wp_cache_add( $cache_key, $cache_value, 'sites' );
 		} else {
 			$site_ids = $cache_value['site_ids'];
 			$this->found_sites = $cache_value['found_sites'];
-			$this->max_num_pages = $cache_value['max_num_pages'];
 		}
 
+		if ( $this->found_sites && $this->query_vars['number'] ) {
+			$this->max_num_pages = ceil( $this->found_sites / $this->query_vars['number'] );
+		}
+
 		// If querying for a count only, there's nothing more to do.
 		if ( $this->query_vars['count'] ) {
 			// $site_ids is actually a count in this case.
@@ -588,7 +590,6 @@
 			$found_sites_query = apply_filters( 'found_sites_query', 'SELECT FOUND_ROWS()', $this );
 
 			$this->found_sites = (int) $wpdb->get_var( $found_sites_query );
-			$this->max_num_pages = ceil( $this->found_sites / $this->query_vars['number'] );
 		}
 	}