diff --git a/PKHeX.Core/Editing/ShowdownSet.cs b/PKHeX.Core/Editing/ShowdownSet.cs
index 998d3699d..55d690549 100644
--- a/PKHeX.Core/Editing/ShowdownSet.cs
+++ b/PKHeX.Core/Editing/ShowdownSet.cs
@@ -189,6 +189,8 @@ private void ParseLines(IEnumerable<string> lines)
                     int move = StringUtil.FindIndexIgnoreCase(Strings.movelist, moveString);
                     if (move < 0)
                         InvalidLines.Add($"Unknown Move: {moveString}");
+                    else if (Moves.Contains(move))
+                        InvalidLines.Add($"Duplicate Move: {moveString}");
                     else
                         Moves[movectr++] = move;
 
diff --git a/Tests/PKHeX.Core.Tests/Simulator/ShowdownSetTests.cs b/Tests/PKHeX.Core.Tests/Simulator/ShowdownSetTests.cs
index e610fcf0c..a6d88bea1 100644
--- a/Tests/PKHeX.Core.Tests/Simulator/ShowdownSetTests.cs
+++ b/Tests/PKHeX.Core.Tests/Simulator/ShowdownSetTests.cs
@@ -1,5 +1,6 @@
 using System;
 using System.Linq;
+using FluentAssertions;
 using PKHeX.Core;
 using Xunit;
 
@@ -157,6 +158,26 @@ public void SimulatorParseMultiple()
             Assert.True(!sets.Any());
         }
 
+        [Theory]
+        [InlineData(SetDuplicateMoves, 3)]
+        public void SimulatorParseDuplicate(string text, int moveCount)
+        {
+            var set = new ShowdownSet(text);
+            var actual = set.Moves.Count(z => z != 0);
+            actual.Should().Be(moveCount);
+        }
+
+        private const string SetDuplicateMoves =
+@"Kingler-Gmax @ Master Ball
+Ability: Sheer Force
+Shiny: Yes
+EVs: 252 Atk / 4 SpD / 252 Spe
+Jolly Nature
+- Crabhammer
+- Rock Slide
+- Rock Slide
+- X-Scissor";
+
         private const string SetROCKSMetang =
 @"Metang
 IVs: 20 HP / 3 Atk / 26 Def / 1 SpA / 6 SpD / 8 Spe