diff --git a/lignumis/scripts/to-nauvis.lua b/lignumis/scripts/to-nauvis.lua
index f9aed80..7dfbd82 100644
--- a/lignumis/scripts/to-nauvis.lua
+++ b/lignumis/scripts/to-nauvis.lua
@@ -58,7 +58,7 @@ end
 
 
 ToNauvis.events[defines.events.on_rocket_launched] = function(event)
-    if event.rocket_silo.name ~= "provisional-rocket-silo" then return end
+    if not event.rocket_silo or event.rocket_silo.name ~= "provisional-rocket-silo" then return end
 
     local rocket_entry
     local rocket_entry_index