1 files changed, 1 insertions, 1 deletions

diff --git a/src/test/Example.Extension/ExamplePreprocessorExtensionAndCommandLine.cs b/src/test/Example.Extension/ExamplePreprocessorExtensionAndCommandLine.cs
index 49f68de5..7244798a 100644
--- a/src/test/Example.Extension/ExamplePreprocessorExtensionAndCommandLine.cs
+++ b/src/test/Example.Extension/ExamplePreprocessorExtensionAndCommandLine.cs
@@ -12,7 +12,7 @@ namespace Example.Extension
     {
         private string exampleValueFromCommandLine;
 
-        public IEnumerable<ExtensionCommandLineSwitch> CommandLineSwitches => throw new NotImplementedException();
+        public IReadOnlyCollection<ExtensionCommandLineSwitch> CommandLineSwitches => throw new NotImplementedException();
 
         public ExamplePreprocessorExtensionAndCommandLine()
         {