diff --git a/Sharpasonne.Tests/Rules/UniqueTileInstanceRuleTests.cs b/Sharpasonne.Tests/Rules/UniqueTileInstanceRuleTests.cs
index c6a81dd..fc139e2 100644
--- a/Sharpasonne.Tests/Rules/UniqueTileInstanceRuleTests.cs
+++ b/Sharpasonne.Tests/Rules/UniqueTileInstanceRuleTests.cs
@@ -1,4 +1,7 @@
-using Sharpasonne.GameActions;
+using System.Collections.Generic;
+using System.Linq;
+using Sharpasonne.GameActions;
+using Sharpasonne.Models;
 using Sharpasonne.Rules;
 using Xunit;
 
@@ -9,7 +12,26 @@ public class UniqueTileInstanceRuleTests : UnitTest<PlaceTileGameAction>
         [Fact]
         public void When_BoardIsEmpty_Then_True()
         {
-            AssertTrue<UniqueTileInstanceRule>(new Engine(), MakePlaceTile(0, 0));
+            this.AssertTrue<UniqueTileInstanceRule>(new Engine(), this.MakePlaceTile(0, 0));
+        }
+
+        [Fact]
+        public void Given_BoardHasInstanceofTile_When_PlaceSameInstanceAgain_Then_False()
+        {
+            var action = MakePlaceTile(0, 0);
+            var board = new[] { action }.ToDictionary(
+                a => a.Point,
+                a => a.Placement
+            );
+
+            var engine = this.MockEngine(new Board(board));
+
+            var secondPlaceTileGameAction = new PlaceTileGameAction(
+                new Point(0, 0),
+                new Placement(action.Placement.Tile, Orientation.Top)
+            );
+
+            this.AssertFalse<UniqueTileInstanceRule>(engine, secondPlaceTileGameAction);
         }
     }
 }
diff --git a/Sharpasonne/Rules/UniqueTileInstanceRule.cs b/Sharpasonne/Rules/UniqueTileInstanceRule.cs
index 8447663..6919e68 100644
--- a/Sharpasonne/Rules/UniqueTileInstanceRule.cs
+++ b/Sharpasonne/Rules/UniqueTileInstanceRule.cs
@@ -1,3 +1,4 @@
+using System.Linq;
 using Sharpasonne.GameActions;
 
 namespace Sharpasonne.Rules
@@ -6,7 +7,13 @@ public class UniqueTileInstanceRule : IRule<PlaceTileGameAction>
     {
         public bool Verify<T1>(IEngine engine, T1 gameAction) where T1 : PlaceTileGameAction
         {
-            return true;
+            var allTiles = engine.Board
+                .ToImmutableDictionary()
+                .Values
+                .Select(placement => placement.Tile);
+
+            return !allTiles
+                .Contains(gameAction.Placement.Tile);
         }
     }
 }