diff --git a/Mage.Sets/src/mage/cards/m/ManaCache.java b/Mage.Sets/src/mage/cards/m/ManaCache.java
index 6094d2a9ba2..c60a2bb3b96 100644
--- a/Mage.Sets/src/mage/cards/m/ManaCache.java
+++ b/Mage.Sets/src/mage/cards/m/ManaCache.java
@@ -127,7 +127,7 @@ class ManaCacheManaAbility extends ActivatedManaAbilityImpl {
             return false;
         }
         Player player = game.getPlayer(playerId);
-        if (player != null && playerId == game.getActivePlayerId() && game.getStep().getType().isBefore(PhaseStep.END_TURN)) {
+        if (player != null && playerId.equals(game.getActivePlayerId()) && game.getStep().getType().isBefore(PhaseStep.END_TURN)) {
             if (costs.canPay(this, sourceId, playerId, game)) {
                 this.setControllerId(playerId);
                 return true;
diff --git a/Mage.Sets/src/mage/cards/m/Martyrdom.java b/Mage.Sets/src/mage/cards/m/Martyrdom.java
index 129b444ddad..a1c38fa9461 100644
--- a/Mage.Sets/src/mage/cards/m/Martyrdom.java
+++ b/Mage.Sets/src/mage/cards/m/Martyrdom.java
@@ -132,7 +132,7 @@ class MartyrdomActivatedAbility extends ActivatedAbilityImpl {
 
     @Override
     public boolean canActivate(UUID playerId, Game game) {
-        if (playerId == caster) {
+        if (playerId.equals(caster)) {
             Permanent permanent = game.getBattlefield().getPermanent(this.getSourceId());
             if (permanent != null) {
                 if (filter.match(permanent, permanent.getId(), permanent.getControllerId(), game)) {
diff --git a/Mage/src/main/java/mage/abilities/SpellAbility.java b/Mage/src/main/java/mage/abilities/SpellAbility.java
index 289fa05592e..dc723dad6c6 100644
--- a/Mage/src/main/java/mage/abilities/SpellAbility.java
+++ b/Mage/src/main/java/mage/abilities/SpellAbility.java
@@ -100,7 +100,7 @@ public class SpellAbility extends ActivatedAbilityImpl {
             // fix for Gitaxian Probe and casting opponent's spells
             if (!game.getContinuousEffects().asThough(getSourceId(), AsThoughEffectType.PLAY_FROM_NOT_OWN_HAND_ZONE, playerId, game)) {
                 Card card = game.getCard(sourceId);
-                if (!(card != null && card.getOwnerId() == playerId)) {
+                if (!(card != null && card.getOwnerId().equals(playerId))) {
                     return false;
                 }
             }
diff --git a/Mage/src/main/java/mage/game/GameImpl.java b/Mage/src/main/java/mage/game/GameImpl.java
index 572a2a4307b..07d14912ec7 100644
--- a/Mage/src/main/java/mage/game/GameImpl.java
+++ b/Mage/src/main/java/mage/game/GameImpl.java
@@ -3058,7 +3058,7 @@ public abstract class GameImpl implements Game, Serializable {
 
     @Override
     public void setMonarchId(Ability source, UUID monarchId) {
-        if (monarchId == getMonarchId()) { // Nothing happens if you're already the monarch
+        if (monarchId.equals(getMonarchId())) { // Nothing happens if you're already the monarch
             return;
         }
         Player newMonarch = getPlayer(monarchId);
diff --git a/Mage/src/main/java/mage/watchers/common/CastSpellYourLastTurnWatcher.java b/Mage/src/main/java/mage/watchers/common/CastSpellYourLastTurnWatcher.java
index 1a3ae1a5ca1..c0f275488a8 100644
--- a/Mage/src/main/java/mage/watchers/common/CastSpellYourLastTurnWatcher.java
+++ b/Mage/src/main/java/mage/watchers/common/CastSpellYourLastTurnWatcher.java
@@ -63,7 +63,7 @@ public class CastSpellYourLastTurnWatcher extends Watcher {
         lastActivePlayer = game.getActivePlayerId();
         if (event.getType() == GameEvent.EventType.SPELL_CAST) {
             UUID playerId = event.getPlayerId();
-            if (playerId != null && lastActivePlayer != null && playerId == lastActivePlayer) {
+            if (playerId != null && lastActivePlayer != null && playerId.equals(lastActivePlayer)) {
                 amountOfSpellsCastOnCurrentTurn.putIfAbsent(playerId, 0);
                 amountOfSpellsCastOnCurrentTurn.compute(playerId, (k, a) -> a + 1);
             }