diff --git a/Source/Game/Spells/SpellInfo.cs b/Source/Game/Spells/SpellInfo.cs
index 60418a986..bbc072aba 100644
--- a/Source/Game/Spells/SpellInfo.cs
+++ b/Source/Game/Spells/SpellInfo.cs
@@ -2714,6 +2714,7 @@ namespace Game.Spells
 
                 // Base powerCost
                 int powerCost = power.ManaCost;
+                bool initiallyNegative = powerCost < 0;
                 // PCT cost from total amount
                 if (power.PowerCostPct != 0)
                 {
@@ -2847,6 +2848,10 @@ namespace Game.Spells
                     continue;
                 }
 
+                // power cost cannot become negative if initially positive
+                if (initiallyNegative != (powerCost < 0))
+                    powerCost = 0;
+
                 bool found = false;
                 for (var i = 0; i < costs.Count; ++i)
                 {