--- a/src/jdk.compiler/share/classes/com/sun/tools/javac/code/Symtab.java	Wed Nov 13 21:56:28 2019 +0800
+++ b/src/jdk.compiler/share/classes/com/sun/tools/javac/code/Symtab.java	Wed Nov 13 10:33:00 2019 -0800
@@ -785,6 +785,7 @@
         unnamedPackage.modle = module;
         //we cannot use a method reference below, as initialCompleter might be null now
         unnamedPackage.completer = s -> initialCompleter.complete(s);
+        unnamedPackage.flags_field |= EXISTS;
         module.unnamedPackage = unnamedPackage;
     }
 

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test/langtools/tools/javac/api/TestModuleUnnamedPackage.java	Wed Nov 13 10:33:00 2019 -0800
@@ -0,0 +1,89 @@
+/*
+ * Copyright (c) 2019, 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     8234025
+ * @summary Elements.getPackageElement(ModuleElement,CharSequence) returns null for unnamed package
+ * @modules jdk.compiler
+ * @library /tools/lib /tools/javac/lib
+ * @build toolbox.ModuleBuilder toolbox.ToolBox
+ * @run main TestModuleUnnamedPackage
+ */
+
+import java.io.IOException;
+import java.nio.file.Path;
+import java.util.List;
+import java.util.Set;
+
+import javax.annotation.processing.RoundEnvironment;
+import javax.lang.model.element.ModuleElement;
+import javax.lang.model.element.PackageElement;
+import javax.lang.model.element.TypeElement;
+import javax.lang.model.util.Elements;
+import javax.tools.JavaCompiler;
+import javax.tools.JavaFileObject;
+import javax.tools.StandardJavaFileManager;
+import javax.tools.StandardLocation;
+import javax.tools.ToolProvider;
+
+import com.sun.source.util.JavacTask;
+import toolbox.Assert;
+import toolbox.ToolBox;
+
+public class TestModuleUnnamedPackage extends JavacTestingAbstractProcessor {
+    public static void main(String... args) throws IOException {
+        TestModuleUnnamedPackage t = new TestModuleUnnamedPackage();
+            t.run();
+    }
+
+    void run() throws IOException {
+        ToolBox tb = new ToolBox();
+        Path src = Path.of("src");
+
+        tb.writeJavaFiles(src, "module m { exports p; }",
+                "package p; public class C { }");
+
+        JavaCompiler c = ToolProvider.getSystemJavaCompiler();
+        StandardJavaFileManager fm = c.getStandardFileManager(null, null, null);
+        fm.setLocationFromPaths(StandardLocation.SOURCE_PATH, List.of(src));
+        List<String> options = List.of("-proc:only");
+        Iterable<? extends JavaFileObject> files = fm.getJavaFileObjects(tb.findJavaFiles(src));
+        JavacTask t = (JavacTask) c.getTask(null, fm, null, null, null, files);
+        t.setProcessors(List.of(this));
+        t.call();
+    }
+
+    public boolean process(Set<? extends TypeElement> elems, RoundEnvironment rEnv) {
+        if (rEnv.processingOver()) {
+            Elements elements = processingEnv.getElementUtils();
+            ModuleElement m = elements.getModuleElement("m");
+            PackageElement unnamed = elements.getPackageElement(m, "");
+            System.out.println("module m: " + m);
+            System.out.println("module m, unnamed package: " + unnamed);
+            Assert.checkNonNull(unnamed, "unnamed package in module m");
+        }
+        return true;
+    }
+}
+