diff --git a/lib/vmpooler/api/v1.rb b/lib/vmpooler/api/v1.rb
index bc599fe..4bd9852 100644
--- a/lib/vmpooler/api/v1.rb
+++ b/lib/vmpooler/api/v1.rb
@@ -387,6 +387,7 @@ module Vmpooler
           status 404
         end
       else
+        metrics.increment('checkout.invalid.unknown')
         status 404
       end
 
@@ -429,6 +430,7 @@ module Vmpooler
           status 404
         end
       else
+        metrics.increment('checkout.invalid.unknown')
         status 404
       end