diff --git a/plugins/synced_folders/rsync/command/rsync_auto.rb b/plugins/synced_folders/rsync/command/rsync_auto.rb
index 3d3cd226c..8bb658c5d 100644
--- a/plugins/synced_folders/rsync/command/rsync_auto.rb
+++ b/plugins/synced_folders/rsync/command/rsync_auto.rb
@@ -42,7 +42,14 @@ module VagrantPlugins
           paths = {}
           ignores = []
           with_target_vms(argv) do |machine|
-            folders = synced_folders(machine)[:rsync]
+            cached = synced_folders(machine, cached: true)
+            fresh  = synced_folders(machine)
+            diff   = synced_folders_diff(cached, fresh)
+            if !diff[:added].empty?
+              machine.ui.warn(I18n.t("vagrant.rsync_auto_new_folders"))
+            end
+
+            folders = cached[:rsync]
             next if !folders || folders.empty?
 
             # Get the SSH info for this machine so we can do an initial
diff --git a/templates/locales/en.yml b/templates/locales/en.yml
index 31c0ff85a..5db009598 100644
--- a/templates/locales/en.yml
+++ b/templates/locales/en.yml
@@ -174,6 +174,10 @@ en:
       Running cleanup tasks for '%{name}' provisioner...
     rsync_auto_initial: |-
       Doing an initial rsync...
+    rsync_auto_new_folders: |-
+      New synced folders were added to the Vagrantfile since running
+      `vagrant reload`. If these new synced folders are backed by rsync,
+      they won't be automatically synced until a `vagrant reload` is run.
     rsync_auto_no_paths: |-
       There are no paths to watch! This is either because you have no
       synced folders using rsync, or any rsync synced folders you have