diff --git a/core/src/main/java/com/shatteredpixel/shatteredpixeldungeon/actors/mobs/Mob.java b/core/src/main/java/com/shatteredpixel/shatteredpixeldungeon/actors/mobs/Mob.java
index 39663c35b..c0abf6bcd 100644
--- a/core/src/main/java/com/shatteredpixel/shatteredpixeldungeon/actors/mobs/Mob.java
+++ b/core/src/main/java/com/shatteredpixel/shatteredpixeldungeon/actors/mobs/Mob.java
@@ -543,8 +543,7 @@ public abstract class Mob extends Char {
 			hitWithRanged = true;
 		}
 		
-		if ((!enemySeen || enemy.invisible > 0)
-				&& enemy == Dungeon.hero && Dungeon.hero.canSurpriseAttack()) {
+		if (surprisedBy(enemy) && Dungeon.hero.canSurpriseAttack()) {
 			Statistics.sneakAttacks++;
 			Badges.validateRogueUnlock();
 			Sample.INSTANCE.play(Assets.Sounds.HIT_STRONG);
@@ -579,7 +578,7 @@ public abstract class Mob extends Char {
 	}
 
 	public boolean surprisedBy( Char enemy ){
-		return (!enemySeen || enemy.invisible > 0) && enemy == Dungeon.hero;
+		return enemy == Dungeon.hero && (enemy.invisible > 0 || (!enemySeen && state != PASSIVE));
 	}
 
 	public void aggro( Char ch ) {
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 3896899f8..950b1b9ac 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
@@ -112,10 +112,7 @@ public class YogDzewa extends Mob {
 
 	@Override
 	protected boolean act() {
-		//catches an error-case from 0.8.0 & 0.8.0a
-		if (!isAlive()){
-			die(null);
-		}
+		enemySeen = true;
 
 		if (phase == 0){
 			if (Dungeon.hero.viewDistance >= Dungeon.level.distance(pos, Dungeon.hero.pos)) {