Index: src/wp-includes/class-wp-network-query.php
===================================================================
--- src/wp-includes/class-wp-network-query.php	(revision 37899)
+++ src/wp-includes/class-wp-network-query.php	(working copy)
@@ -229,15 +229,17 @@
 			$cache_value = array(
 				'network_ids' => $network_ids,
 				'found_networks' => $this->found_networks,
-				'max_num_pages' => $this->max_num_pages,
 			);
 			wp_cache_add( $cache_key, $cache_value, 'networks' );
 		} else {
 			$network_ids = $cache_value['network_ids'];
 			$this->found_networks = $cache_value['found_networks'];
-			$this->max_num_pages = $cache_value['max_num_pages'];
 		}
 
+		if ( $this->found_networks && $this->query_vars['number'] ) {
+			$this->max_num_pages = ceil( $this->found_networks / $this->query_vars['number'] );
+		}
+		
 		// If querying for a count only, there's nothing more to do.
 		if ( $this->query_vars['count'] ) {
 			// $network_ids is actually a count in this case.
@@ -477,7 +479,6 @@
 			$found_networks_query = apply_filters( 'found_networks_query', 'SELECT FOUND_ROWS()', $this );
 
 			$this->found_networks = (int) $wpdb->get_var( $found_networks_query );
-			$this->max_num_pages = ceil( $this->found_networks / $this->query_vars['number'] );
 		}
 	}