diff --git a/code/modules/antagonists/vampire/vampire_powers/umbrae_powers.dm b/code/modules/antagonists/vampire/vampire_powers/umbrae_powers.dm
index ddfd83028a3..a91f2038ba4 100644
--- a/code/modules/antagonists/vampire/vampire_powers/umbrae_powers.dm
+++ b/code/modules/antagonists/vampire/vampire_powers/umbrae_powers.dm
@@ -184,7 +184,7 @@
 	var/datum/spell_handler/vampire/V = custom_handler
 	var/datum/antagonist/vampire/vampire = user.mind.has_antag_datum(/datum/antagonist/vampire)
 	var/blood_cost = V.calculate_blood_cost(vampire)
-	vampire.bloodusable -= blood_cost
+	vampire.bloodusable = clamp(vampire.bloodusable - blood_cost, 0, vampire.bloodusable)// Vampires get a coupon if they have less than the normal blood cost
 	addtimer(VARSET_CALLBACK(src, should_recharge_after_cast, FALSE), 1 SECONDS) // this is needed so that the spell handler knows we casted it properly
 
 /proc/shadow_to_animation(turf/start_turf, turf/end_turf, mob/user)