--- old/src/java.desktop/share/classes/javax/imageio/spi/DigraphNode.java	2019-09-21 12:30:24.791000000 -0700
+++ new/src/java.desktop/share/classes/javax/imageio/spi/DigraphNode.java	2019-09-21 12:30:24.591000000 -0700
@@ -43,12 +43,14 @@
     private static final long serialVersionUID = 5308261378582246841L;
 
     /** The data associated with this node. */
+    @SuppressWarnings("serial") // Not statically typed as Serializable
     protected E data;
 
     /**
      * A {@code Set} of neighboring nodes pointed to by this
      * node.
      */
+    @SuppressWarnings("serial") // Not statically typed as Serializable
     protected Set<DigraphNode<E>> outNodes = new HashSet<>();
 
     /** The in-degree of the node. */
@@ -58,6 +60,7 @@
      * A {@code Set} of neighboring nodes that point to this
      * node.
      */
+    @SuppressWarnings("serial") // Not statically typed as Serializable
     private Set<DigraphNode<E>> inNodes = new HashSet<>();
 
     public DigraphNode(E data) {