diff --git a/code/modules/reagents/Chemistry-Machinery.dm b/code/modules/reagents/Chemistry-Machinery.dm
index b54c87c78f..9db39f296b 100644
--- a/code/modules/reagents/Chemistry-Machinery.dm
+++ b/code/modules/reagents/Chemistry-Machinery.dm
@@ -104,7 +104,7 @@
   *
   * @return nothing
   */
-/obj/machinery/chem_dispenser/ui_interact(mob/user, ui_key = "main")
+/obj/machinery/chem_dispenser/ui_interact(mob/user, ui_key = "main",var/datum/nanoui/ui = null)
 	if(broken_requirements.len)
 		user << "<span class='warning'>[src] is broken. [broken_requirements[broken_requirements[1]]]</span>"
 		return