diff --git a/mo_gymnasium/envs/deep_sea_treasure/deep_sea_treasure.py b/mo_gymnasium/envs/deep_sea_treasure/deep_sea_treasure.py
index 374c15a0..479a880b 100644
--- a/mo_gymnasium/envs/deep_sea_treasure/deep_sea_treasure.py
+++ b/mo_gymnasium/envs/deep_sea_treasure/deep_sea_treasure.py
@@ -212,10 +212,16 @@ def _get_map_value(self, pos):
         return self.sea_map[pos[0]][pos[1]]
 
     def _is_valid_state(self, state):
-        if state[0] >= 0 and state[0] <= 10 and state[1] >= 0 and state[1] <= 10:
-            if self._get_map_value(state) != -10:
-                return True
-        return False
+        if self.map_name == "mirrored":
+            if state[0] >= 0 and state[0] <= 10 and state[1] >= 0 and state[1] <= 19:
+                if self._get_map_value(state) != -10:
+                    return True
+            return False
+        else:
+            if state[0] >= 0 and state[0] <= 10 and state[1] >= 0 and state[1] <= 10:
+                if self._get_map_value(state) != -10:
+                    return True
+            return False
 
     def render(self):
         if self.render_mode is None: