diff --git a/jdk/src/java.base/share/classes/javax/security/auth/Subject.java b/jdk/src/java.base/share/classes/javax/security/auth/Subject.java
index 4e4e61cc0ed..e570eb6686f 100644
--- a/jdk/src/java.base/share/classes/javax/security/auth/Subject.java
+++ b/jdk/src/java.base/share/classes/javax/security/auth/Subject.java
@@ -1522,17 +1522,20 @@ public final class Subject implements java.io.Serializable {
             }
         }
 
+        @Override
         public int size() {
             return set.size();
         }
 
+        @Override
         public Iterator<T> iterator() {
             return set.iterator();
         }
 
+        @Override
         public boolean add(T o) {
 
-            if (!o.getClass().isAssignableFrom(c)) {
+            if (!c.isAssignableFrom(o.getClass())) {
                 MessageFormat form = new MessageFormat(ResourcesMgr.getString
                         ("attempting.to.add.an.object.which.is.not.an.instance.of.class"));
                 Object[] source = {c.toString()};
diff --git a/jdk/test/javax/security/auth/Subject/AddPrincipalSubclass.java b/jdk/test/javax/security/auth/Subject/AddPrincipalSubclass.java
new file mode 100644
index 00000000000..4fa4014384a
--- /dev/null
+++ b/jdk/test/javax/security/auth/Subject/AddPrincipalSubclass.java
@@ -0,0 +1,66 @@
+/*
+ * Copyright (c) 2015, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * @test
+ * @bug 8034820
+ * @summary Check that adding Principal subclasses to Subject works
+ */
+
+import java.security.Principal;
+import java.util.Collections;
+import java.util.Set;
+import javax.security.auth.Subject;
+
+public class AddPrincipalSubclass {
+
+    public static void main(String[] args) throws Exception {
+
+        // create Subject with no principals and then add TestPrincipal
+        Subject subject = new Subject();
+        Set<Principal> principals = subject.getPrincipals(Principal.class);
+        Principal principal = new TestPrincipal();
+        if (!principals.add(principal)) {
+            throw new Exception("add returned false instead of true");
+        }
+        if (!principals.contains(principal)) {
+            throw new Exception("set does not contain principal");
+        }
+
+        // pre-populate Subject with TestPrincipal
+        subject = new Subject(false,
+                              Collections.singleton(principal),
+                              Collections.emptySet(), Collections.emptySet());
+        principals = subject.getPrincipals(Principal.class);
+        if (!principals.contains(principal)) {
+            throw new Exception("set does not contain principal");
+        }
+    }
+
+    private static class TestPrincipal implements Principal {
+        @Override
+        public String getName() {
+            return "TestPrincipal";
+        }
+    }
+}