diff --git a/src/main/scala/com/wordnik/swagger/model/SwaggerModelSerializer.scala b/src/main/scala/com/wordnik/swagger/model/SwaggerModelSerializer.scala
index d2aff8ee7b1..8b63333f07d 100644
--- a/src/main/scala/com/wordnik/swagger/model/SwaggerModelSerializer.scala
+++ b/src/main/scala/com/wordnik/swagger/model/SwaggerModelSerializer.scala
@@ -87,6 +87,7 @@ object SwaggerSerializers {
           new ResourceListingSerializer +
           new ApiListingSerializer
       }
+      case _ => throw new IllegalArgumentException("%s is not a valid Swagger version".format(version))
     }
   }