diff --git a/wp-admin/includes/ajax-actions.php b/wp-admin/includes/ajax-actions.php
index 59c1736ef1..8aca23eccd 100644
--- a/wp-admin/includes/ajax-actions.php
+++ b/wp-admin/includes/ajax-actions.php
@@ -2904,7 +2904,10 @@ function wp_ajax_install_plugin() {
 	}
 
 	$plugin_status = install_plugin_install_status( $api );
-	activate_plugin( $plugin_status['file'] );
+
+	if ( ! is_multisite() ) {
+		activate_plugin( $plugin_status['file'] );
+	}
 
 	wp_send_json_success( $status );
 }
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 4ba4c54f7b..4efd3bbd2f 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.2-alpha-31510';
+$wp_version = '4.2-alpha-31511';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.