diff --git a/Source/monster.cpp b/Source/monster.cpp
index f003d66d7..e3e9e6488 100644
--- a/Source/monster.cpp
+++ b/Source/monster.cpp
@@ -3338,7 +3338,7 @@ tl::expected<void, std::string> GetLevelMTypes()
 		_monster_id typelist[MaxMonsters];
 
 		int nt = 0;
-		for (int i = MT_NZOMBIE; i < NUM_MTYPES; i++) {
+		for (size_t i = 0; i < MonstersData.size(); i++) {
 			if (!IsMonsterAvalible(MonstersData[i]))
 				continue;