diff --git a/classpath/java/lang/Number.java b/classpath/java/lang/Number.java
index 1e3b2d55a3..a1563014be 100644
--- a/classpath/java/lang/Number.java
+++ b/classpath/java/lang/Number.java
@@ -10,7 +10,9 @@
 
 package java.lang;
 
-public abstract class Number {
+import java.io.Serializable;
+
+public abstract class Number implements Serializable {
   public abstract byte byteValue();
   public abstract short shortValue();
   public abstract int intValue();