--- a/src/hotspot/share/classfile/classLoader.hpp	Tue Sep 26 17:06:06 2017 +0200
+++ b/src/hotspot/share/classfile/classLoader.hpp	Tue Sep 26 15:34:49 2017 +0000
@@ -403,7 +403,8 @@
   static int compute_Object_vtable();
 
   static ClassPathEntry* classpath_entry(int n) {
-    assert(n >= 0 && n < _num_entries, "sanity");
+    assert(n >= 0, "sanity");
+    assert(!has_jrt_entry() || n < _num_entries, "sanity");
     if (n == 0) {
       assert(has_jrt_entry(), "No class path entry at 0 for exploded module builds");
       return ClassLoader::_jrt_entry;

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test/hotspot/jtreg/runtime/getSysPackage/GetPackageXbootclasspath.java	Tue Sep 26 15:34:49 2017 +0000
@@ -0,0 +1,59 @@
+/*
+ * Copyright (c) 2017, 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 8187436
+ * @summary Test that getPackage() works with a class loaded via -Xbootclasspath/a.
+ * @library /test/lib
+ * @run main/othervm GetPackageXbootclasspath
+ */
+
+// This is a regression test for a bug with the exploded build but should pass
+// when run with either the normal or exploded build.
+import jdk.test.lib.compiler.InMemoryJavaCompiler;
+import jdk.test.lib.process.ProcessTools;
+import jdk.test.lib.process.OutputAnalyzer;
+
+public class GetPackageXbootclasspath {
+
+    public static void main(String args[]) throws Exception {
+
+        String Test_src =
+            "package P; " +
+            "public class Test { " +
+                "public static void main(String[] args) throws Exception { " +
+                    "Package p = Test.class.getPackage(); " +
+                    "System.out.println(\"Test Passed\"); " +
+                "} " +
+            "}";
+
+        String test_classes = System.getProperty("test.classes");
+        ClassFileInstaller.writeClassToDisk("P/Test",
+            InMemoryJavaCompiler.compile("P.Test", Test_src), test_classes);
+
+        new OutputAnalyzer(ProcessTools.createJavaProcessBuilder(
+                "-Xbootclasspath/a:" + test_classes, "P.Test")
+            .start()).shouldContain("Test Passed");
+    }
+}