diff --git a/middleman-core/lib/middleman-core/preview_server.rb b/middleman-core/lib/middleman-core/preview_server.rb
index 068c9334..27152706 100644
--- a/middleman-core/lib/middleman-core/preview_server.rb
+++ b/middleman-core/lib/middleman-core/preview_server.rb
@@ -81,6 +81,10 @@ module Middleman
         end
 
         unmount_instance
+
+        @webrick.shutdown
+        @webrick = nil
+
         mount_instance(app)
 
         logger.info '== The Middleman has reloaded'