diff --git a/advtrains/lzb.lua b/advtrains/lzb.lua
index efbce66..afbf68e 100644
--- a/advtrains/lzb.lua
+++ b/advtrains/lzb.lua
@@ -172,7 +172,7 @@ function advtrains.lzb_add_checkpoint(train, index, speed, callback, udata)
 		idx = index,
 		spd = speed,
 		fun = callback,
-		data = udata,
+		udata = udata,
 	})
 end
 
diff --git a/advtrains/wagons.lua b/advtrains/wagons.lua
index 381f835..12fd74e 100644
--- a/advtrains/wagons.lua
+++ b/advtrains/wagons.lua
@@ -927,8 +927,8 @@ function wagon:handle_bordcom_fields(pname, formname, fields)
 		local i=1
 		while train.lzb.oncoming[i] do
 			local oci = train.lzb.oncoming[i]
-			if oci.pos then
-				local sigd = advtrains.interlocking.db.get_sigd_for_signal(oci.pos)
+			if oci.udata and oci.udata.signal_pos then
+				local sigd = advtrains.interlocking.db.get_sigd_for_signal(oci.udata.signal_pos)
 				if sigd then
 					advtrains.interlocking.show_signalling_form(sigd, pname)
 					return
diff --git a/advtrains_interlocking/approach.lua b/advtrains_interlocking/approach.lua
index 630ebfe..3fe72f6 100644
--- a/advtrains_interlocking/approach.lua
+++ b/advtrains_interlocking/approach.lua
@@ -105,7 +105,7 @@ advtrains.tnc_register_on_approach(function(pos, id, train, index, lzbdata)
 		
 		local udata = {signal_pos = spos}
 		local callback = get_over_function(lspd, travsht)
-		advtrains.lzb_add_checkpoint(train, index, lspd, callback)
+		advtrains.lzb_add_checkpoint(train, index, lspd, callback, udata)
 	end
 	lzbdata.travsht = travsht
 	lzbdata.travspd = travspd