diff --git a/src/AutoRest.CSharp/Common/Generation/Types/TypeFactory.cs b/src/AutoRest.CSharp/Common/Generation/Types/TypeFactory.cs
index b9f95ba7776..1d021760ac8 100644
--- a/src/AutoRest.CSharp/Common/Generation/Types/TypeFactory.cs
+++ b/src/AutoRest.CSharp/Common/Generation/Types/TypeFactory.cs
@@ -89,7 +89,7 @@ public TypeFactory(OutputLibrary library, Type unknownType)
             },
             InputDateTimeType dateTimeType => new CSharpType(typeof(DateTimeOffset), inputType.IsNullable),
             InputDurationType durationType => new CSharpType(typeof(TimeSpan), inputType.IsNullable),
-            _ => throw new Exception("Unknown type")
+            _ => throw new InvalidOperationException($"Unknown type: {inputType}")
         };
 
         /// <summary>