diff --git a/code/modules/power/apc.dm b/code/modules/power/apc.dm
index e16bcd23b31..b7b320c6006 100644
--- a/code/modules/power/apc.dm
+++ b/code/modules/power/apc.dm
@@ -27,6 +27,7 @@
 #define APC_UPOVERLAY_ENVIRON1 1024
 #define APC_UPOVERLAY_ENVIRON2 2048
 #define APC_UPOVERLAY_LOCKED 4096
+#define APC_UPOVERLAY_OPERATING 8192
 
 
 #define APC_UPDATE_ICON_COOLDOWN 200 // 20 seconds
@@ -302,6 +303,9 @@
 	if(update_state <= 1)
 		update_state |= UPSTATE_ALLGOOD
 
+	if(operating)
+		update_overlay |= APC_UPOVERLAY_OPERATING
+
 	if(update_state & UPSTATE_ALLGOOD)
 		if(locked)
 			update_overlay |= APC_UPOVERLAY_LOCKED
@@ -333,6 +337,7 @@
 			update_overlay |= APC_UPOVERLAY_ENVIRON1
 		else if(environ==2)
 			update_overlay |= APC_UPOVERLAY_ENVIRON2
+	
 
 	var/results = 0
 	if(last_update_state == update_state && last_update_overlay == update_overlay)