diff --git a/src/game.rs b/src/game.rs
index 44c531b..a35a995 100644
--- a/src/game.rs
+++ b/src/game.rs
@@ -54,7 +54,7 @@ pub enum LogSeverity {
     Debug,
 }
 
-const LOG_SEVERITY: LogSeverity = LogSeverity::Basic;
+const LOG_SEVERITY: LogSeverity = LogSeverity::Debug;
 
 impl PlayerColor {
     pub fn swap(&mut self) {
@@ -483,7 +483,7 @@ impl MillGame {
         scene: &mut Scene,
         board: &mut [[[BoardSlot; 3]; 3]; 3],
         state: &mut GameState,
-    ) -> Result<MillState> {
+    ) -> Result<Option<MillState>> {
         Self::log(
             &format!("move stone ({:?}) to ({:?})", (x, y, z), (tx, ty, tz)),
             LogSeverity::Debug,
@@ -492,9 +492,11 @@ impl MillGame {
         let slot = &board[x][y][z];
         let neighbour = &board[tx][ty][tz];
 
-        if neighbour.state() != BoardSlotState::Empty {
+        if neighbour.state() != BoardSlotState::Empty
+            || !Self::is_neighbour((x, y, z), (tx, ty, tz))
+        {
             Self::log("neighbour not empty", LogSeverity::Debug);
-            return Ok(MillState::None);
+            return Ok(None);
         }
 
         neighbour.set_state(slot.state());
@@ -544,7 +546,7 @@ impl MillGame {
             LogSeverity::Debug,
         );
 
-        Ok(millstate)
+        Ok(Some(millstate))
     }
 
     pub fn remove_stone(stone: &mut Stone, slot: &mut BoardSlot, scene: &mut Scene) -> Result<()> {
@@ -822,9 +824,12 @@ impl EngineObject for MillGame {
                                     match *selected_slot {
                                         Some((x, y, z)) => {
                                             if Self::is_neighbour((x, y, z), (tx, ty, tz)) {
-                                                if Self::move_stone((x,y,z), (tx,ty,tz), scene, board, &mut state)? == MillState::None {
-                                                    *selected_slot = None;
-                                                    self.finish_turn();
+                                                if let Some(millstate)
+                                                    = Self::move_stone((x,y,z), (tx,ty,tz), scene, board, &mut state)?  {
+                                                    if let MillState::None = millstate {
+                                                        *selected_slot = None;
+                                                        self.finish_turn();
+                                                    }
                                                 }
                                             }
                                         }
diff --git a/src/simple_ai.rs b/src/simple_ai.rs
index 38c0717..12aee9c 100644
--- a/src/simple_ai.rs
+++ b/src/simple_ai.rs
@@ -129,15 +129,16 @@ impl SimpleAI {
                             let (tx, ty, tz) = (neighbour.x, neighbour.y, neighbour.z);
 
                             scene.on_scene(|scene| {
-                                if MillGame::move_stone(
+                                if let Some(millstate) = MillGame::move_stone(
                                     (x, y, z),
                                     (tx, ty, tz),
                                     scene,
                                     board,
                                     state,
-                                )? != MillState::None
-                                {
-                                    found_a_mill = true;
+                                )? {
+                                    if MillState::None != millstate {
+                                        found_a_mill = true;
+                                    }
                                 }
 
                                 Ok(())