diff --git a/CHANGELOG.md b/CHANGELOG.md
index 769f09bedb..6017f62db4 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,6 +8,7 @@
     Bug #3737: Scripts from The Underground 2 .esp do not play (all patched versions)
     Bug #3792: 1 frame late magicka recalc breaks early scripted magicka reactions to Intelligence change
     Bug #3846: Strings starting with "-" fail to compile if not enclosed in quotes
+    Bug #3855: AI sometimes spams defensive spells
     Bug #3905: Great House Dagoth issues
     Bug #4203: Resurrecting an actor should close the loot GUI
     Bug #4602: Robert's Bodies: crash inside createInstance()
diff --git a/apps/openmw/mwmechanics/spellpriority.cpp b/apps/openmw/mwmechanics/spellpriority.cpp
index eb276deb78..acc9fc2a3f 100644
--- a/apps/openmw/mwmechanics/spellpriority.cpp
+++ b/apps/openmw/mwmechanics/spellpriority.cpp
@@ -368,6 +368,24 @@ namespace MWMechanics
                 return 0.f;
 
             break;
+        case ESM::MagicEffect::BoundShield:
+            if(!actor.getClass().hasInventoryStore(actor))
+                return 0.f;
+            else if(!actor.getClass().isNpc())
+            {
+                // If the actor is an NPC they can benefit from the armor rating, otherwise check if we've got a one-handed weapon to use with the shield
+                const auto& store = actor.getClass().getInventoryStore(actor);
+                auto oneHanded = std::find_if(store.cbegin(MWWorld::ContainerStore::Type_Weapon), store.cend(), [](const MWWorld::ConstPtr& weapon)
+                {
+                    if(weapon.getClass().getItemHealth(weapon) <= 0.f)
+                        return false;
+                    short type = weapon.get<ESM::Weapon>()->mBase->mData.mType;
+                    return !(MWMechanics::getWeaponType(type)->mFlags & ESM::WeaponType::TwoHanded);
+                });
+                if(oneHanded == store.cend())
+                    return 0.f;
+            }
+            break;
         // Creatures can not wear armor
         case ESM::MagicEffect::BoundCuirass:
         case ESM::MagicEffect::BoundGloves:
@@ -552,6 +570,13 @@ namespace MWMechanics
             if (!creatureStats.getSummonedCreatureMap().empty())
                 return 0.f;
         }
+        if(effect.mEffectID >= ESM::MagicEffect::BoundDagger && effect.mEffectID <= ESM::MagicEffect::BoundGloves)
+        {
+            // While rateSpell prevents actors from recasting the same spell, it doesn't prevent them from casting different spells with the same effect.
+            // Multiple instances of the same bound item don't stack so if the effect is already active, rate it as useless.
+            if(actor.getClass().getCreatureStats(actor).getMagicEffects().get(effect.mEffectID).getMagnitude() > 0.f)
+                return 0.f;
+        }
 
         // Underwater casting not possible
         if (effect.mRange == ESM::RT_Target)