diff -r 5af9fa90cd7b -r 48b88b9c11eb src/jdk.javadoc/share/classes/jdk/javadoc/internal/doclets/toolkit/builders/SerializedFormBuilder.java
--- a/src/jdk.javadoc/share/classes/jdk/javadoc/internal/doclets/toolkit/builders/SerializedFormBuilder.java	Wed Nov 27 12:18:40 2019 +0100
+++ b/src/jdk.javadoc/share/classes/jdk/javadoc/internal/doclets/toolkit/builders/SerializedFormBuilder.java	Wed Nov 27 13:08:16 2019 +0100
@@ -96,12 +96,6 @@
     protected Element currentMember;
 
     /**
-     * The content that will be added to the serialized form documentation tree.
-     */
-    private Content contentTree;
-
-
-    /**
      * Construct a new SerializedFormBuilder.
      * @param context  the build context.
      */
@@ -137,32 +131,30 @@
             //Doclet does not support this output.
             return;
         }
-        buildSerializedForm(contentTree);
+        buildSerializedForm();
     }
 
     /**
      * Build the serialized form.
      *
-     * @param serializedTree content tree to which the documentation will be added
      * @throws DocletException if there is a problem while building the documentation
      */
-    protected void buildSerializedForm(Content serializedTree) throws DocletException {
-        serializedTree = writer.getHeader(resources.getText(
+    protected void buildSerializedForm() throws DocletException {
+        Content contentTree = writer.getHeader(resources.getText(
                 "doclet.Serialized_Form"));
 
-        buildSerializedFormSummaries(serializedTree);
+        buildSerializedFormSummaries();
 
-        writer.addFooter(serializedTree);
-        writer.printDocument(serializedTree);
+        writer.addFooter();
+        writer.printDocument(contentTree);
     }
 
     /**
      * Build the serialized form summaries.
      *
-     * @param serializedTree content tree to which the documentation will be added
      * @throws DocletException if there is a problem while building the documentation
      */
-    protected void buildSerializedFormSummaries(Content serializedTree)
+    protected void buildSerializedFormSummaries()
             throws DocletException {
         Content serializedSummariesTree = writer.getSerializedSummariesHeader();
         for (PackageElement pkg : configuration.packages) {
@@ -170,8 +162,7 @@
 
             buildPackageSerializedForm(serializedSummariesTree);
         }
-        serializedTree.add(writer.getSerializedContent(
-                serializedSummariesTree));
+        writer.addSerializedContent(serializedSummariesTree);
     }
 
     /**