diff --git a/code/game/objects/structures/girders.dm b/code/game/objects/structures/girders.dm
index 361c119f9bc..cb7350f5b34 100644
--- a/code/game/objects/structures/girders.dm
+++ b/code/game/objects/structures/girders.dm
@@ -47,7 +47,7 @@
 		new /obj/item/stack/sheet/metal(get_turf(src))
 		qdel(src)
 
-/obj/structure/girder/temperature_expose(gas_mixture/air, exposed_temperature)
+/obj/structure/girder/temperature_expose(datum/gas_mixture/air, exposed_temperature)
 	var/temp_check = exposed_temperature
 	if(temp_check >= GIRDER_MELTING_TEMP)
 		take_damage(10)