diff --git a/src/genieutils/civ.py b/src/genieutils/civ.py
index 3687fe6..a0ea454 100644
--- a/src/genieutils/civ.py
+++ b/src/genieutils/civ.py
@@ -5,7 +5,7 @@
 from genieutils.versions import Version
 
 
-@dataclass
+@dataclass(slots=True)
 class Civ(GenieClass):
     player_type: int
     name: str
diff --git a/src/genieutils/datfile.py b/src/genieutils/datfile.py
index 91487e3..75332c1 100644
--- a/src/genieutils/datfile.py
+++ b/src/genieutils/datfile.py
@@ -18,7 +18,7 @@
 from genieutils.versions import Version
 
 
-@dataclass
+@dataclass(slots=True)
 class DatFile(GenieClass):
     version: str
     float_ptr_terrain_tables: list[int]
diff --git a/src/genieutils/effect.py b/src/genieutils/effect.py
index 24bf511..533bb0c 100644
--- a/src/genieutils/effect.py
+++ b/src/genieutils/effect.py
@@ -4,7 +4,7 @@
 from genieutils.versions import Version
 
 
-@dataclass
+@dataclass(slots=True)
 class EffectCommand(GenieClass):
     type: int
     a: int
@@ -32,7 +32,7 @@ def to_bytes(self, version: Version) -> bytes:
         ])
 
 
-@dataclass
+@dataclass(slots=True)
 class Effect(GenieClass):
     name: str
     effect_commands: list[EffectCommand]
diff --git a/src/genieutils/graphic.py b/src/genieutils/graphic.py
index 9efd1ba..a810de2 100644
--- a/src/genieutils/graphic.py
+++ b/src/genieutils/graphic.py
@@ -4,7 +4,7 @@
 from genieutils.versions import Version
 
 
-@dataclass
+@dataclass(slots=True)
 class GraphicDelta(GenieClass):
     graphic_id: int
     padding_1: int
@@ -38,7 +38,7 @@ def to_bytes(self, version: Version) -> bytes:
         ])
 
 
-@dataclass
+@dataclass(slots=True)
 class GraphicAngleSound(GenieClass):
     frame_num: int
     sound_id: int
@@ -78,7 +78,7 @@ def to_bytes(self, version: Version) -> bytes:
         ])
 
 
-@dataclass
+@dataclass(slots=True)
 class Graphic(GenieClass):
     name: str
     file_name: str
diff --git a/src/genieutils/playercolour.py b/src/genieutils/playercolour.py
index f1c869f..01c3208 100644
--- a/src/genieutils/playercolour.py
+++ b/src/genieutils/playercolour.py
@@ -4,7 +4,7 @@
 from genieutils.versions import Version
 
 
-@dataclass
+@dataclass(slots=True)
 class PlayerColour(GenieClass):
     id: int
     player_color_base: int
diff --git a/src/genieutils/randommaps.py b/src/genieutils/randommaps.py
index 3e5671a..a9f272a 100644
--- a/src/genieutils/randommaps.py
+++ b/src/genieutils/randommaps.py
@@ -4,7 +4,7 @@
 from genieutils.versions import Version
 
 
-@dataclass
+@dataclass(slots=True)
 class MapUnit(GenieClass):
     unit: int
     host_terrain: int
@@ -56,7 +56,7 @@ def to_bytes(self, version: Version) -> bytes:
         ])
 
 
-@dataclass
+@dataclass(slots=True)
 class MapTerrain(GenieClass):
     proportion: int
     terrain: int
@@ -87,7 +87,7 @@ def to_bytes(self, version: Version) -> bytes:
         ])
 
 
-@dataclass
+@dataclass(slots=True)
 class MapLand(GenieClass):
     land_id: int
     terrain: int
@@ -145,7 +145,7 @@ def to_bytes(self, version: Version) -> bytes:
         ])
 
 
-@dataclass
+@dataclass(slots=True)
 class MapElevation(GenieClass):
     proportion: int
     terrain: int
@@ -176,7 +176,7 @@ def to_bytes(self, version: Version) -> bytes:
         ])
 
 
-@dataclass
+@dataclass(slots=True)
 class MapInfo(GenieClass):
     map_id: int
     border_south_west: int
@@ -277,7 +277,7 @@ def to_bytes(self, version: Version) -> bytes:
         ])
 
 
-@dataclass
+@dataclass(slots=True)
 class RandomMaps(GenieClass):
     random_maps_ptr: int
     map_info_1: list[MapInfo]
diff --git a/src/genieutils/sound.py b/src/genieutils/sound.py
index ebe321b..f4f32b3 100644
--- a/src/genieutils/sound.py
+++ b/src/genieutils/sound.py
@@ -4,7 +4,7 @@
 from genieutils.versions import Version
 
 
-@dataclass
+@dataclass(slots=True)
 class SoundItem(GenieClass):
     filename: str
     resource_id: int
@@ -32,7 +32,7 @@ def to_bytes(self, version: Version) -> bytes:
         ])
 
 
-@dataclass
+@dataclass(slots=True)
 class Sound(GenieClass):
     id: int
     play_delay: int
diff --git a/src/genieutils/task.py b/src/genieutils/task.py
index 20b3d83..a68ef48 100644
--- a/src/genieutils/task.py
+++ b/src/genieutils/task.py
@@ -4,7 +4,7 @@
 from genieutils.versions import Version
 
 
-@dataclass
+@dataclass(slots=True)
 class Task(GenieClass):
     task_type: int
     id: int
diff --git a/src/genieutils/tech.py b/src/genieutils/tech.py
index 97ba278..b5b27df 100644
--- a/src/genieutils/tech.py
+++ b/src/genieutils/tech.py
@@ -4,7 +4,7 @@
 from genieutils.versions import Version
 
 
-@dataclass
+@dataclass(slots=True)
 class ResearchResourceCost(GenieClass):
     type: int
     amount: int
@@ -26,7 +26,7 @@ def to_bytes(self, version: Version) -> bytes:
         ])
 
 
-@dataclass
+@dataclass(slots=True)
 class Tech(GenieClass):
     required_techs: tuple[int, int, int, int, int, int]
     resource_costs: tuple[ResearchResourceCost, ResearchResourceCost, ResearchResourceCost]
diff --git a/src/genieutils/techtree.py b/src/genieutils/techtree.py
index eb6cff3..27e6c5f 100644
--- a/src/genieutils/techtree.py
+++ b/src/genieutils/techtree.py
@@ -4,7 +4,7 @@
 from genieutils.versions import Version
 
 
-@dataclass
+@dataclass(slots=True)
 class Common(GenieClass):
     slots_used: int
     unit_research: tuple[int, int, int, int, int, int, int, int, int, int]
@@ -26,7 +26,7 @@ def to_bytes(self, version: Version) -> bytes:
         ])
 
 
-@dataclass
+@dataclass(slots=True)
 class TechTreeAge(GenieClass):
     id: int
     status: int
@@ -89,7 +89,7 @@ def to_bytes(self, version: Version) -> bytes:
         ])
 
 
-@dataclass
+@dataclass(slots=True)
 class BuildingConnection(GenieClass):
     id: int
     status: int
@@ -152,7 +152,7 @@ def to_bytes(self, version: Version) -> bytes:
         ])
 
 
-@dataclass
+@dataclass(slots=True)
 class UnitConnection(GenieClass):
     id: int
     status: int
@@ -207,7 +207,7 @@ def to_bytes(self, version: Version) -> bytes:
         ])
 
 
-@dataclass
+@dataclass(slots=True)
 class ResearchConnection(GenieClass):
     id: int
     status: int
@@ -266,7 +266,7 @@ def to_bytes(self, version: Version) -> bytes:
         ])
 
 
-@dataclass
+@dataclass(slots=True)
 class TechTree(GenieClass):
     total_unit_tech_groups: int
     tech_tree_ages: list[TechTreeAge]
diff --git a/src/genieutils/terrainblock.py b/src/genieutils/terrainblock.py
index 6629e1f..83686e8 100644
--- a/src/genieutils/terrainblock.py
+++ b/src/genieutils/terrainblock.py
@@ -4,7 +4,7 @@
 from genieutils.versions import Version
 
 
-@dataclass
+@dataclass(slots=True)
 class FrameData(GenieClass):
     frame_count: int
     angle_count: int
@@ -26,7 +26,7 @@ def to_bytes(self, version: Version) -> bytes:
         ])
 
 
-@dataclass
+@dataclass(slots=True)
 class Terrain(GenieClass):
     enabled: int
     random: int
@@ -153,7 +153,7 @@ def to_bytes(self, version: Version) -> bytes:
         ])
 
 
-@dataclass
+@dataclass(slots=True)
 class TileSize(GenieClass):
     width: int
     height: int
@@ -175,7 +175,7 @@ def to_bytes(self, version: Version) -> bytes:
         ])
 
 
-@dataclass
+@dataclass(slots=True)
 class TerrainBlock(GenieClass):
     virtual_function_ptr: int
     map_pointer: int
diff --git a/src/genieutils/terrainrestriction.py b/src/genieutils/terrainrestriction.py
index 1f1d52e..cd9ff42 100644
--- a/src/genieutils/terrainrestriction.py
+++ b/src/genieutils/terrainrestriction.py
@@ -4,7 +4,7 @@
 from genieutils.versions import Version
 
 
-@dataclass
+@dataclass(slots=True)
 class TerrainPassGraphic(GenieClass):
     exit_tile_sprite_id: int
     enter_tile_sprite_id: int
@@ -29,7 +29,7 @@ def to_bytes(self, version: Version) -> bytes:
         ])
 
 
-@dataclass
+@dataclass(slots=True)
 class TerrainRestriction(GenieClass):
     passable_buildable_dmg_multiplier: list[float]
     terrain_pass_graphics: list[TerrainPassGraphic]
diff --git a/src/genieutils/unit.py b/src/genieutils/unit.py
index 3b8fff0..1b569a5 100644
--- a/src/genieutils/unit.py
+++ b/src/genieutils/unit.py
@@ -5,7 +5,7 @@
 from genieutils.versions import Version
 
 
-@dataclass
+@dataclass(slots=True)
 class ResourceStorage(GenieClass):
     type: int
     amount: float
@@ -27,7 +27,7 @@ def to_bytes(self, version: Version) -> bytes:
         ])
 
 
-@dataclass
+@dataclass(slots=True)
 class DamageGraphic(GenieClass):
     graphic_id: int
     damage_percent: int
@@ -49,7 +49,7 @@ def to_bytes(self, version: Version) -> bytes:
         ])
 
 
-@dataclass
+@dataclass(slots=True)
 class DeadFish(GenieClass):
     walking_graphic: int
     running_graphic: int
@@ -104,7 +104,7 @@ def to_bytes(self, version: Version) -> bytes:
         ])
 
 
-@dataclass
+@dataclass(slots=True)
 class Bird(GenieClass):
     default_task_id: int
     search_radius: float
@@ -167,7 +167,7 @@ def to_bytes(self, version: Version) -> bytes:
         ])
 
 
-@dataclass
+@dataclass(slots=True)
 class AttackOrArmor(GenieClass):
     class_: int
     amount: int
@@ -186,7 +186,7 @@ def to_bytes(self, version: Version) -> bytes:
         ])
 
 
-@dataclass
+@dataclass(slots=True)
 class Type50(GenieClass):
     base_armor: int
     attacks: list[AttackOrArmor]
@@ -291,7 +291,7 @@ def to_bytes(self, version: Version) -> bytes:
         ])
 
 
-@dataclass
+@dataclass(slots=True)
 class Projectile(GenieClass):
     projectile_type: int
     smart_mode: int
@@ -322,7 +322,7 @@ def to_bytes(self, version: Version) -> bytes:
         ])
 
 
-@dataclass
+@dataclass(slots=True)
 class ResourceCost(GenieClass):
     type: int
     amount: int
@@ -344,7 +344,7 @@ def to_bytes(self, version: Version) -> bytes:
         ])
 
 
-@dataclass
+@dataclass(slots=True)
 class Creatable(GenieClass):
     resource_costs: tuple[ResourceCost, ResourceCost, ResourceCost]
     train_time: int
@@ -435,7 +435,7 @@ def to_bytes(self, version: Version) -> bytes:
         ])
 
 
-@dataclass
+@dataclass(slots=True)
 class BuildingAnnex(GenieClass):
     unit_id: int
     misplacement_x: float
@@ -457,7 +457,7 @@ def to_bytes(self, version: Version) -> bytes:
         ])
 
 
-@dataclass
+@dataclass(slots=True)
 class Building(GenieClass):
     construction_graphic_id: int
     snow_graphic_id: int
@@ -548,7 +548,7 @@ def to_bytes(self, version: Version) -> bytes:
         ])
 
 
-@dataclass
+@dataclass(slots=True)
 class Unit(GenieClass):
     type: int
     id: int
diff --git a/src/genieutils/unitheaders.py b/src/genieutils/unitheaders.py
index 13e61d2..d5f853d 100644
--- a/src/genieutils/unitheaders.py
+++ b/src/genieutils/unitheaders.py
@@ -5,14 +5,13 @@
 from genieutils.versions import Version
 
 
-@dataclass
+@dataclass(slots=True)
 class UnitHeaders(GenieClass):
     exists: int
     task_list: list[Task] | None = None
 
     @classmethod
     def from_bytes(cls, content: ByteHandler) -> 'UnitHeaders':
-        super().__init__(content)
         exists = content.read_int_8()
         task_list = None
         if exists:
diff --git a/tests/test_common.py b/tests/test_common.py
index 446f86d..3a021a2 100644
--- a/tests/test_common.py
+++ b/tests/test_common.py
@@ -101,7 +101,7 @@ def byte_handler_class(self):
     
     @pytest.fixture
     def child_genie_class(self):
-        @dataclasses.dataclass
+        @dataclasses.dataclass(slots=True)
         class ChildGenieClass(GenieClass):
             int_8_val: int
             int_16_val: int