1 files changed, 5 insertions, 2 deletions

diff --git a/src/WixToolset.Core/ExtensibilityServices/TupleDefinitionCreator.cs b/src/WixToolset.Core/ExtensibilityServices/TupleDefinitionCreator.cs
index b442da2b..e223e3a4 100644
--- a/src/WixToolset.Core/ExtensibilityServices/TupleDefinitionCreator.cs
+++ b/src/WixToolset.Core/ExtensibilityServices/TupleDefinitionCreator.cs
@@ -1,4 +1,4 @@
-// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
 
 namespace WixToolset.Core.ExtensibilityServices
 {
@@ -23,7 +23,10 @@ namespace WixToolset.Core.ExtensibilityServices
 
         public void AddCustomTupleDefinition(IntermediateTupleDefinition definition)
         {
-            this.CustomDefinitionByName.Add(definition.Name, definition);
+            if (!this.CustomDefinitionByName.TryGetValue(definition.Name, out var existing) || definition.Revision > existing.Revision)
+            {
+                this.CustomDefinitionByName[definition.Name] = definition;
+            }
         }
 
         public bool TryGetTupleDefinitionByName(string name, out IntermediateTupleDefinition tupleDefinition)