diff --git a/middleman-core/lib/middleman-core/preview_server.rb b/middleman-core/lib/middleman-core/preview_server.rb
index e89e552f..dddaf21b 100644
--- a/middleman-core/lib/middleman-core/preview_server.rb
+++ b/middleman-core/lib/middleman-core/preview_server.rb
@@ -71,6 +71,10 @@ module Middleman
         end
 
         unmount_instance
+
+        @webrick.shutdown
+        @webrick = nil
+
         mount_instance(app)
 
         logger.info '== The Middleman has reloaded'