diff --git a/cli/src/main/scala/scalaxb/compiler/xsd/GenSource.scala b/cli/src/main/scala/scalaxb/compiler/xsd/GenSource.scala
index 6444c2c75..b04e730f1 100644
--- a/cli/src/main/scala/scalaxb/compiler/xsd/GenSource.scala
+++ b/cli/src/main/scala/scalaxb/compiler/xsd/GenSource.scala
@@ -146,7 +146,7 @@ class GenSource(val schema: SchemaDecl,
       }
     }
 
-    val traitCode = <source>{ buildComment(decl) }trait {localName}{extendString} {{
+    val traitCode = <source>{ buildComment(decl) }sealed trait {localName}{extendString} {{
   {
   val vals = paramList.flatMap(paramEntries)
   vals.mkString(newline + indent(1))}