diff --git a/pantheon.php b/pantheon.php
index 7bd9168..c94afed 100644
--- a/pantheon.php
+++ b/pantheon.php
@@ -40,6 +40,11 @@
 		 */
 		define( 'FS_METHOD', 'direct' );
 	}
+    // When developing a WordPress Multisite locally, ensure that this constant is set.
+    // This will set the Multisite variable in all Pantheon environments.
+    if ( getenv( 'FRAMEWORK' ) === 'wordpress_network' && ! defined( 'WP_ALLOW_MULTISITE' ) ) {
+        define( 'WP_ALLOW_MULTISITE', true );
+    }
     if ( defined( 'WP_ALLOW_MULTISITE' ) && ( ! defined( 'MULTISITE' ) || empty( MULTISITE ) ) ) {
         require_once 'inc/pantheon-multisite-finalize.php';
     }