1 files changed, 1 insertions, 1 deletions

diff --git a/src/WixToolset.Core.ExtensionCache/ExtensionCacheManagerExtensionCommandLine.cs b/src/WixToolset.Core.ExtensionCache/ExtensionCacheManagerExtensionCommandLine.cs
index 76587830..2a603adf 100644
--- a/src/WixToolset.Core.ExtensionCache/ExtensionCacheManagerExtensionCommandLine.cs
+++ b/src/WixToolset.Core.ExtensionCache/ExtensionCacheManagerExtensionCommandLine.cs
@@ -21,7 +21,7 @@ namespace WixToolset.Core.ExtensionCache
 
         private IServiceProvider ServiceProvider { get; }
 
-        public override IEnumerable<ExtensionCommandLineSwitch> CommandLineSwitches => new ExtensionCommandLineSwitch[]
+        public override IReadOnlyCollection<ExtensionCommandLineSwitch> CommandLineSwitches => new ExtensionCommandLineSwitch[]
         {
             new ExtensionCommandLineSwitch { Switch = "extension", Description = "Manage extension cache." },
         };