--- a/src/java.base/share/classes/java/net/ServerSocket.java	Tue May 07 16:06:10 2019 +0200
+++ b/src/java.base/share/classes/java/net/ServerSocket.java	Tue May 07 15:39:33 2019 +0100
@@ -32,6 +32,7 @@
 import java.nio.channels.ServerSocketChannel;
 import java.security.AccessController;
 import java.security.PrivilegedExceptionAction;
+import java.util.Objects;
 import java.util.Set;
 import java.util.Collections;
 
@@ -81,6 +82,7 @@
      * @since 12
      */
     protected ServerSocket(SocketImpl impl) {
+        Objects.requireNonNull(impl);
         this.impl = impl;
     }