diff --git a/code/datums/ammo/ammo.dm b/code/datums/ammo/ammo.dm
index c29a96c02a86..f2a7dc8ffc81 100644
--- a/code/datums/ammo/ammo.dm
+++ b/code/datums/ammo/ammo.dm
@@ -175,8 +175,8 @@
 /datum/ammo/proc/slowdown(mob/living/living_mob, obj/projectile/fired_projectile)
 	if(isxeno(living_mob))
 		var/mob/living/carbon/xenomorph/xeno = living_mob
-		if(xeno.caste.tier > 2)
-			return //tier 3 are not affected
+		if(xeno.caste.tier > 2 || (xeno.caste.tier == 0 && xeno.mob_size >= MOB_SIZE_BIG))
+			return //tier 3 and big tier 0 (like queen) are not affected
 	if(iscarbonsizexeno(living_mob))
 		var/mob/living/carbon/xenomorph/target = living_mob
 		target.apply_effect(1, SUPERSLOW)