diff --git a/lib/manageiq/network_discovery/discovery.rb b/lib/manageiq/network_discovery/discovery.rb
index 7792f9ff4f2f..9344c2f4c57e 100644
--- a/lib/manageiq/network_discovery/discovery.rb
+++ b/lib/manageiq/network_discovery/discovery.rb
@@ -29,6 +29,7 @@ def self.scan_host(ost)
         end
 
         if ping
+          raise ArgumentError, "must pass discover_types" if ost.discover_types.nil?
           # Trigger probes
           ost.discover_types.each do |type|
             next unless PROVIDERS_BY_TYPE.include?(type)