diff --git a/code/controllers/subsystem/timer.dm b/code/controllers/subsystem/timer.dm
index 9bd56294c69..7be217ffe71 100644
--- a/code/controllers/subsystem/timer.dm
+++ b/code/controllers/subsystem/timer.dm
@@ -579,8 +579,8 @@ SUBSYSTEM_DEF(timer)
  * * timer_subsystem the subsystem to insert this timer into
  */
 /proc/_addtimer(datum/callback/callback, wait = 0, flags = 0, datum/controller/subsystem/timer/timer_subsystem, file, line)
-	if (!callback)
-		CRASH("addtimer called without a callback")
+	ASSERT(istype(callback), "addtimer called [callback ? "with an invalid callback ([callback])" : "without a callback"]")
+	ASSERT(isnum(wait), "addtimer called with a non-numeric wait ([wait])")
 
 	if (wait < 0)
 		stack_trace("addtimer called with a negative wait. Converting to [world.tick_lag]")
diff --git a/code/modules/mob/mob.dm b/code/modules/mob/mob.dm
index 51e6de5d49b..28a58b38558 100644
--- a/code/modules/mob/mob.dm
+++ b/code/modules/mob/mob.dm
@@ -1036,7 +1036,7 @@
 
 	mob_light(range = 2, color = antimagic_color, duration = 5 SECONDS)
 	add_overlay(antimagic_effect)
-	addtimer(CALLBACK(src, TYPE_PROC_REF(/atom, cut_overlay)), antimagic_effect, 5 SECONDS)
+	addtimer(CALLBACK(src, TYPE_PROC_REF(/atom, cut_overlay), antimagic_effect), 5 SECONDS)
 
 /**
  * Buckle a living mob to this mob. Also turns you to face the other mob