diff --git a/src/rail_cmd.cpp b/src/rail_cmd.cpp
--- a/src/rail_cmd.cpp
+++ b/src/rail_cmd.cpp
@@ -1054,8 +1054,8 @@ static CommandCost CmdSignalTrackHelper(
 	track = TrackdirToTrack(trackdir); /* trackdir might have changed, keep track in sync */
 	Trackdir start_trackdir = trackdir;
 
-	/* Autofill must start on a valid track to be able to avoid loops */
-	if (autofill && !HasTrack(tile, track)) return CMD_ERROR;
+	/* Must start on a valid track to be able to avoid loops */
+	if (!HasTrack(tile, track)) return CMD_ERROR;
 
 	SignalType sigtype = (SignalType)GB(p2, 7, 3);
 	if (sigtype > SIGTYPE_LAST) return CMD_ERROR;