diff --git a/Cargo.toml b/Cargo.toml
index da69c63..a94d2ec 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "mapgen"
-version = "0.1.2"
+version = "0.2.0"
 authors = ["Krzysztof Langner <klangner@gmail.com>"]
 description = "Map generator for games (dungeons, worlds etc.)"
 keywords = ["game", "map", "map-generator"]
diff --git a/demo/src/lib.rs b/demo/src/lib.rs
index 00f8817..1d0c0f9 100644
--- a/demo/src/lib.rs
+++ b/demo/src/lib.rs
@@ -31,7 +31,7 @@ pub struct World {
 impl World {
     pub fn new_cellular_automata(width: u32, height: u32, seed: u32) -> World {
         let mut rng = StdRng::seed_from_u64(seed as u64);
-        let map = MapBuilder::new(Box::new(CellularAutomataGen::new()))
+        let map = MapBuilder::new(CellularAutomataGen::new())
             .with(AreaStartingPosition::new(XStart::CENTER, YStart::CENTER))
             .with(CullUnreachable::new())
             .with(DistantExit::new())
@@ -47,7 +47,7 @@ impl World {
 
     pub fn new_random_rooms(width: u32, height: u32, seed: u32) -> World {
         let mut rng = StdRng::seed_from_u64(seed as u64);
-        let map = MapBuilder::new(Box::new(RandomRoomsGen::new()))
+        let map = MapBuilder::new(RandomRoomsGen::new())
             .with(NearestCorridors::new())
             .build_map_with_rng(width as usize, height as usize, &mut rng);
         let tiles = (0..map.tiles.len())
diff --git a/src/dungeon/cellular_automata.rs b/src/dungeon/cellular_automata.rs
index 38a972f..f05b103 100644
--- a/src/dungeon/cellular_automata.rs
+++ b/src/dungeon/cellular_automata.rs
@@ -39,8 +39,8 @@ impl MapGenerator for CellularAutomataGen {
 
 impl CellularAutomataGen {
     /// Create generator which will create map with the given dimension.
-    pub fn new() -> CellularAutomataGen {
-        CellularAutomataGen {}
+    pub fn new() -> Box<CellularAutomataGen> {
+        Box::new(CellularAutomataGen {})
     }
 
     /// Generate map
diff --git a/src/dungeon/mod.rs b/src/dungeon/mod.rs
index 96ca7a1..8e00cce 100644
--- a/src/dungeon/mod.rs
+++ b/src/dungeon/mod.rs
@@ -16,7 +16,7 @@
 //!     starting_point::{AreaStartingPosition, XStart, YStart},
 //! };
 //! 
-//! let map = MapBuilder::new(Box::new(CellularAutomataGen::new()))
+//! let map = MapBuilder::new(CellularAutomataGen::new())
 //!             .with(AreaStartingPosition::new(XStart::CENTER, YStart::CENTER))
 //!             .build_map(80, 50);
 //! 
@@ -104,7 +104,7 @@ mod tests {
 
     #[test]
     fn test_ca_map() {
-        let map = MapBuilder::new(Box::new(CellularAutomataGen::new()))
+        let map = MapBuilder::new(CellularAutomataGen::new())
             .with(AreaStartingPosition::new(XStart::CENTER, YStart::CENTER))
             .build_map(80, 50);
 
diff --git a/src/dungeon/random_rooms.rs b/src/dungeon/random_rooms.rs
index 0b0e84d..b54d4c3 100644
--- a/src/dungeon/random_rooms.rs
+++ b/src/dungeon/random_rooms.rs
@@ -40,12 +40,12 @@ impl MapGenerator for RandomRoomsGen {
 
 
 impl RandomRoomsGen {
-    pub fn new() -> RandomRoomsGen {
-        RandomRoomsGen{
+    pub fn new() -> Box<RandomRoomsGen> {
+        Box::new(RandomRoomsGen{
             max_rooms: 30,
             min_room_size: 6,
             max_room_size: 10
-        }
+        })
     }
 
     fn build_rooms(&self, width: usize, height: usize, rng : &mut StdRng) -> Map {