diff --git a/config/initializers/logster.rb b/config/initializers/logster.rb
index 9176d258a..607d7a6de 100644
--- a/config/initializers/logster.rb
+++ b/config/initializers/logster.rb
@@ -5,6 +5,8 @@ if Rails.env.production?
 
     /^PG::Error: ERROR:\s+duplicate key/,
 
+    /^ActionController::UnknownFormat/,
+
     # suppress trackback spam bots
     Logster::IgnorePattern.new("Can't verify CSRF token authenticity", { REQUEST_URI: /\/trackback\/$/ })
   ]