2 files changed, 23 insertions, 12 deletions
diff --git a/src/server/game/Entities/Creature/Creature.cpp b/src/server/game/Entities/Creature/Creature.cpp
index 5742404926f..46993d92e09 100644
--- a/src/server/game/Entities/Creature/Creature.cpp
+++ b/src/server/game/Entities/Creature/Creature.cpp
@@ -555,6 +555,7 @@ bool Creature::UpdateEntry(uint32 entry, CreatureData const* data /*= nullptr*/,
 
     UpdateMovementFlags();
     LoadCreaturesAddon();
+    LoadMechanicTemplateImmunity();
     return true;
 }
 
@@ -1905,9 +1906,28 @@ void Creature::DespawnOrUnsummon(uint32 msTimeToDespawn /*= 0*/, Seconds const&
         ForcedDespawn(msTimeToDespawn, forceRespawnTimer);
 }
 
-bool Creature::HasMechanicTemplateImmunity(uint32 mask) const
+void Creature::LoadMechanicTemplateImmunity()
 {
-    return (!GetOwnerGUID().IsPlayer() || !IsHunterPet()) && (GetCreatureTemplate()->MechanicImmuneMask & mask);
+    // uint32 max used for "spell id", the immunity system will not perform SpellInfo checks against invalid spells
+    // used so we know which immunities were loaded from template
+    static uint32 const placeholderSpellId = std::numeric_limits<uint32>::max();
+
+    // unapply template immunities (in case we're updating entry)
+    for (uint32 i = MECHANIC_NONE + 1; i < MAX_MECHANIC; ++i)
+        ApplySpellImmune(placeholderSpellId, IMMUNITY_MECHANIC, i, false);
+
+    // don't inherit immunities for hunter pets
+    if (GetOwnerGUID().IsPlayer() && IsHunterPet())
+        return;
+
+    if (uint32 mask = GetCreatureTemplate()->MechanicImmuneMask)
+    {
+        for (uint32 i = MECHANIC_NONE + 1; i < MAX_MECHANIC; ++i)
+        {
+            if (mask & (1 << (i - 1)))
+                ApplySpellImmune(placeholderSpellId, IMMUNITY_MECHANIC, i, true);
+        }
+    }
 }
 
 bool Creature::IsImmunedToSpell(SpellInfo const* spellInfo, Unit* caster) const
@@ -1915,12 +1935,6 @@ bool Creature::IsImmunedToSpell(SpellInfo const* spellInfo, Unit* caster) const
     if (!spellInfo)
         return false;
 
-    // Creature is immune to main mechanic of the spell
-    if (spellInfo->Mechanic > MECHANIC_NONE && HasMechanicTemplateImmunity(1 << (spellInfo->Mechanic - 1)))
-        return true;
-
-    // This check must be done instead of 'if (GetCreatureTemplate()->MechanicImmuneMask & (1 << (spellInfo->Mechanic - 1)))' for not break
-    // the check of mechanic immunity on DB (tested) because GetCreatureTemplate()->MechanicImmuneMask and m_spellImmune[IMMUNITY_MECHANIC] don't have same data.
     bool immunedToAllEffects = true;
     for (uint8 i = 0; i < MAX_SPELL_EFFECTS; ++i)
     {
@@ -1939,9 +1953,6 @@ bool Creature::IsImmunedToSpell(SpellInfo const* spellInfo, Unit* caster) const
 
 bool Creature::IsImmunedToSpellEffect(SpellInfo const* spellInfo, uint32 index, Unit* caster) const
 {
-    if (spellInfo->Effects[index].Mechanic > MECHANIC_NONE && HasMechanicTemplateImmunity(1 << (spellInfo->Effects[index].Mechanic - 1)))
-        return true;
-
     if (GetCreatureTemplate()->type == CREATURE_TYPE_MECHANICAL && spellInfo->Effects[index].Effect == SPELL_EFFECT_HEAL)
         return true;
 
diff --git a/src/server/game/Entities/Creature/Creature.h b/src/server/game/Entities/Creature/Creature.h
index fd00f63635f..1fc9833e376 100644
--- a/src/server/game/Entities/Creature/Creature.h
+++ b/src/server/game/Entities/Creature/Creature.h
@@ -478,7 +478,7 @@ class TC_GAME_API Creature : public Unit, public GridObject<Creature>, public Ma
         bool isCanInteractWithBattleMaster(Player* player, bool msg) const;
         bool isCanTrainingAndResetTalentsOf(Player* player) const;
         bool CanCreatureAttack(Unit const* victim, bool force = true) const;
-        bool HasMechanicTemplateImmunity(uint32 mask) const;
+        void LoadMechanicTemplateImmunity();
         bool IsImmunedToSpell(SpellInfo const* spellInfo, Unit* caster) const override;
         bool IsImmunedToSpellEffect(SpellInfo const* spellInfo, uint32 index, Unit* caster) const override;
         bool isElite() const;