diff --git a/planet/src/world_manager.rs b/planet/src/world_manager.rs
index f9ee94b..4d8440b 100644
--- a/planet/src/world_manager.rs
+++ b/planet/src/world_manager.rs
@@ -160,8 +160,8 @@ impl WorldManager {
         self.get_world().unwrap()
     }
 
-    pub fn new_world(&mut self) -> Result<&World, WorldGenError> {
-        let seed = random();
+    pub fn new_world(&mut self, seed: Option<u32>) -> Result<&World, WorldGenError> {
+        let seed = seed.unwrap_or_else(random);
         let mut new_world = World::new(400, 200, seed);
         new_world.generate()?;
         self.world = Some(new_world);
diff --git a/src/gui/widgets/toolbar.rs b/src/gui/widgets/toolbar.rs
index 3b05e35..7a2c4f4 100644
--- a/src/gui/widgets/toolbar.rs
+++ b/src/gui/widgets/toolbar.rs
@@ -34,7 +34,7 @@ impl ToolbarButton {
         world.resource_scope(|world, mut world_manager: Mut<'_, WorldManager>| {
             match self {
                 ToolbarButton::GenerateWorld => {
-                    if let Err(err) = world_manager.new_world() {
+                    if let Err(err) = world_manager.new_world(None) {
                         eprintln!("Failed to generate world: {}", err);
                     } else {
                         world.resource_mut::<ShouldRedraw>().0 = true;
diff --git a/src/main.rs b/src/main.rs
index 6c3dc4e..aa9db4d 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -252,7 +252,7 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
     let mut manager = WorldManager::new();
     #[cfg(feature = "render")]
     {
-        let world = manager.new_world()?;
+        let world = manager.new_world(None)?;
         _ = app
             .insert_resource(WinitSettings::game())
             // Use nearest-neighbor rendering for cripsier pixels