diff --git a/src/main/java/com/threerings/presents/tools/GenActionScriptStreamableTask.java b/src/main/java/com/threerings/presents/tools/GenActionScriptStreamableTask.java
index c5b187991..27481c7e2 100644
--- a/src/main/java/com/threerings/presents/tools/GenActionScriptStreamableTask.java
+++ b/src/main/java/com/threerings/presents/tools/GenActionScriptStreamableTask.java
@@ -134,7 +134,7 @@ public class GenActionScriptStreamableTask extends GenTask
 
         String template = sclass.isEnum() ? "enum_as.tmpl" : "streamable_as.tmpl";
         String output = mergeTemplate("com/threerings/presents/tools/" + template,
-            "header", _header,
+            "header", existing == null ? _header : "",
             "package", sclass.getPackage().getName(),
             "classname", ActionScriptUtils.toSimpleName(sclass),
             "imports", imports.toList(),
diff --git a/src/main/resources/com/threerings/presents/tools/enum_as.tmpl b/src/main/resources/com/threerings/presents/tools/enum_as.tmpl
index 80643ed75..fb4eabd85 100644
--- a/src/main/resources/com/threerings/presents/tools/enum_as.tmpl
+++ b/src/main/resources/com/threerings/presents/tools/enum_as.tmpl
@@ -1,5 +1,4 @@
-// GENERATED PREAMBLE START
-{{header}}
+{{header}}// GENERATED PREAMBLE START
 package {{package}} {
 
 {{#imports}}
diff --git a/src/main/resources/com/threerings/presents/tools/streamable_as.tmpl b/src/main/resources/com/threerings/presents/tools/streamable_as.tmpl
index 2a3e7c8a2..aa7d08ae4 100644
--- a/src/main/resources/com/threerings/presents/tools/streamable_as.tmpl
+++ b/src/main/resources/com/threerings/presents/tools/streamable_as.tmpl
@@ -1,5 +1,4 @@
-// GENERATED PREAMBLE START
-{{header}}
+{{header}}// GENERATED PREAMBLE START
 package {{package}} {
 
 {{#imports}}