diff --git a/core/src/main/java/com/shatteredpixel/shatteredpixeldungeon/actors/mobs/DM300.java b/core/src/main/java/com/shatteredpixel/shatteredpixeldungeon/actors/mobs/DM300.java
index dae5dc08f..f15f89181 100644
--- a/core/src/main/java/com/shatteredpixel/shatteredpixeldungeon/actors/mobs/DM300.java
+++ b/core/src/main/java/com/shatteredpixel/shatteredpixeldungeon/actors/mobs/DM300.java
@@ -476,7 +476,7 @@ public class DM300 extends Mob {
 		int dmgTaken = preHP - HP;
 		if (dmgTaken > 0) {
 			LockedFloor lock = Dungeon.hero.buff(LockedFloor.class);
-			if (lock != null && !isImmune(src.getClass())){
+			if (lock != null && !isImmune(src.getClass()) && !isInvulnerable(src.getClass())){
 				if (Dungeon.isChallenged(Challenges.STRONGER_BOSSES))   lock.addTime(dmgTaken/2f);
 				else                                                    lock.addTime(dmgTaken);
 			}
diff --git a/core/src/main/java/com/shatteredpixel/shatteredpixeldungeon/actors/mobs/DwarfKing.java b/core/src/main/java/com/shatteredpixel/shatteredpixeldungeon/actors/mobs/DwarfKing.java
index 05ecfb1cb..f078b91bb 100644
--- a/core/src/main/java/com/shatteredpixel/shatteredpixeldungeon/actors/mobs/DwarfKing.java
+++ b/core/src/main/java/com/shatteredpixel/shatteredpixeldungeon/actors/mobs/DwarfKing.java
@@ -476,7 +476,7 @@ public class DwarfKing extends Mob {
 		super.damage(dmg, src);
 
 		LockedFloor lock = Dungeon.hero.buff(LockedFloor.class);
-		if (lock != null && !isImmune(src.getClass())){
+		if (lock != null && !isImmune(src.getClass()) && !isInvulnerable(src.getClass())){
 			if (Dungeon.isChallenged(Challenges.STRONGER_BOSSES))   lock.addTime(dmg/5f);
 			else                                                    lock.addTime(dmg/3f);
 		}
diff --git a/core/src/main/java/com/shatteredpixel/shatteredpixeldungeon/actors/mobs/Goo.java b/core/src/main/java/com/shatteredpixel/shatteredpixeldungeon/actors/mobs/Goo.java
index fb8637053..1f6bf89ad 100644
--- a/core/src/main/java/com/shatteredpixel/shatteredpixeldungeon/actors/mobs/Goo.java
+++ b/core/src/main/java/com/shatteredpixel/shatteredpixeldungeon/actors/mobs/Goo.java
@@ -273,7 +273,7 @@ public class Goo extends Mob {
 			yell(Messages.get(this, "gluuurp"));
 		}
 		LockedFloor lock = Dungeon.hero.buff(LockedFloor.class);
-		if (lock != null){
+		if (lock != null && !isImmune(src.getClass()) && !isInvulnerable(src.getClass())){
 			if (Dungeon.isChallenged(Challenges.STRONGER_BOSSES))   lock.addTime(dmg);
 			else                                                    lock.addTime(dmg*1.5f);
 		}
diff --git a/core/src/main/java/com/shatteredpixel/shatteredpixeldungeon/actors/mobs/Pylon.java b/core/src/main/java/com/shatteredpixel/shatteredpixeldungeon/actors/mobs/Pylon.java
index 2b64b9283..6a3f747f3 100644
--- a/core/src/main/java/com/shatteredpixel/shatteredpixeldungeon/actors/mobs/Pylon.java
+++ b/core/src/main/java/com/shatteredpixel/shatteredpixeldungeon/actors/mobs/Pylon.java
@@ -203,7 +203,7 @@ public class Pylon extends Mob {
 		}
 
 		LockedFloor lock = Dungeon.hero.buff(LockedFloor.class);
-		if (lock != null && !isImmune(src.getClass())){
+		if (lock != null && !isImmune(src.getClass()) && !isInvulnerable(src.getClass())){
 			if (Dungeon.isChallenged(Challenges.STRONGER_BOSSES))   lock.addTime(dmg/2f);
 			else                                                    lock.addTime(dmg);
 		}
diff --git a/core/src/main/java/com/shatteredpixel/shatteredpixeldungeon/actors/mobs/Tengu.java b/core/src/main/java/com/shatteredpixel/shatteredpixeldungeon/actors/mobs/Tengu.java
index 87fceb3e5..2f823e585 100644
--- a/core/src/main/java/com/shatteredpixel/shatteredpixeldungeon/actors/mobs/Tengu.java
+++ b/core/src/main/java/com/shatteredpixel/shatteredpixeldungeon/actors/mobs/Tengu.java
@@ -153,7 +153,7 @@ public class Tengu extends Mob {
 		dmg = beforeHitHP - HP;
 
 		LockedFloor lock = Dungeon.hero.buff(LockedFloor.class);
-		if (lock != null) {
+		if (lock != null && !isImmune(src.getClass()) && !isInvulnerable(src.getClass())){
 			if (Dungeon.isChallenged(Challenges.STRONGER_BOSSES))   lock.addTime(2*dmg/3f);
 			else                                                    lock.addTime(dmg);
 		}
diff --git a/core/src/main/java/com/shatteredpixel/shatteredpixeldungeon/actors/mobs/YogDzewa.java b/core/src/main/java/com/shatteredpixel/shatteredpixeldungeon/actors/mobs/YogDzewa.java
index 5aea77c74..b03a3ade4 100644
--- a/core/src/main/java/com/shatteredpixel/shatteredpixeldungeon/actors/mobs/YogDzewa.java
+++ b/core/src/main/java/com/shatteredpixel/shatteredpixeldungeon/actors/mobs/YogDzewa.java
@@ -422,7 +422,7 @@ public class YogDzewa extends Mob {
 		}
 
 		LockedFloor lock = Dungeon.hero.buff(LockedFloor.class);
-		if (lock != null){
+		if (lock != null && !isImmune(src.getClass()) && !isInvulnerable(src.getClass())){
 			if (Dungeon.isChallenged(Challenges.STRONGER_BOSSES))   lock.addTime(dmgTaken/3f);
 			else                                                    lock.addTime(dmgTaken/2f);
 		}
diff --git a/core/src/main/java/com/shatteredpixel/shatteredpixeldungeon/actors/mobs/YogFist.java b/core/src/main/java/com/shatteredpixel/shatteredpixeldungeon/actors/mobs/YogFist.java
index 67130d205..136239b53 100644
--- a/core/src/main/java/com/shatteredpixel/shatteredpixeldungeon/actors/mobs/YogFist.java
+++ b/core/src/main/java/com/shatteredpixel/shatteredpixeldungeon/actors/mobs/YogFist.java
@@ -152,7 +152,7 @@ public abstract class YogFist extends Mob {
 		int dmgTaken = preHP - HP;
 
 		LockedFloor lock = Dungeon.hero.buff(LockedFloor.class);
-		if (dmgTaken > 0 && lock != null){
+		if (dmgTaken > 0 && lock != null && !isImmune(src.getClass()) && !isInvulnerable(src.getClass())){
 			if (Dungeon.isChallenged(Challenges.STRONGER_BOSSES))   lock.addTime(dmgTaken/4f);
 			else                                                    lock.addTime(dmgTaken/2f);
 		}