--- a/src/java.base/share/classes/java/net/DelegatingSocketImpl.java	Sun Feb 10 19:51:43 2019 +0000
+++ b/src/java.base/share/classes/java/net/DelegatingSocketImpl.java	Mon Feb 11 08:39:50 2019 +0000
@@ -31,6 +31,8 @@
 import java.util.Objects;
 import java.util.Set;
 
+import sun.net.TrustedSocketImpl;
+
 /**
  * A SocketImpl that delegates all methods to another SocketImpl.
  */
@@ -39,6 +41,7 @@
     protected final SocketImpl delegate;
 
     DelegatingSocketImpl(SocketImpl delegate) {
+        assert delegate instanceof TrustedSocketImpl;
         this.delegate = Objects.requireNonNull(delegate);
     }