diff --git a/code/modules/nano/modules/alarm_monitor.dm b/code/modules/nano/modules/alarm_monitor.dm
index 9047023bf1b..b27349bf9a8 100644
--- a/code/modules/nano/modules/alarm_monitor.dm
+++ b/code/modules/nano/modules/alarm_monitor.dm
@@ -85,7 +85,7 @@
 					"origin_lost" = A.origin == null,
 					"has_cameras" = cameras.len,
 					"cameras" = cameras,
-					"lost_sources" = sanitize(english_list(lost_sources, nothing_text = "", and_text = ", "))))
+					"lost_sources" = lost_sources.len ? sanitize(english_list(lost_sources, nothing_text = "", and_text = ", ")) : ""))
 	data["categories"] = categories
 
 	ui = nanomanager.try_update_ui(user, src, ui_key, ui, data, force_open)