diff --git a/src/main/java/com/android/tools/r8/Version.java b/src/main/java/com/android/tools/r8/Version.java
index 30db140..5b36379 100644
--- a/src/main/java/com/android/tools/r8/Version.java
+++ b/src/main/java/com/android/tools/r8/Version.java
@@ -11,7 +11,7 @@
 
   // This field is accessed from release scripts using simple pattern matching.
   // Therefore, changing this field could break our release scripts.
-  public static final String LABEL = "1.4.27";
+  public static final String LABEL = "1.4.28";
 
   private Version() {
   }
diff --git a/src/main/java/com/android/tools/r8/naming/ClassNameMinifier.java b/src/main/java/com/android/tools/r8/naming/ClassNameMinifier.java
index ad084e4..b02801c 100644
--- a/src/main/java/com/android/tools/r8/naming/ClassNameMinifier.java
+++ b/src/main/java/com/android/tools/r8/naming/ClassNameMinifier.java
@@ -473,6 +473,11 @@
           .toCharArray();
       this.packageDictionaryIterator = packageDictionary.iterator();
       this.classDictionaryIterator = classDictionary.iterator();
+
+      // R.class in Android, which contains constant IDs to assets, can be bundled at any time.
+      // Insert `R` immediately so that the class name minifier can skip that name by default.
+      StringBuilder rBuilder = new StringBuilder().append(packagePrefix).append("R;");
+      usedTypeNames.add(appInfo.dexItemFactory.createString(rBuilder.toString()));
     }
 
     public String getPackageName() {
diff --git a/src/test/java/com/android/tools/r8/naming/AvoidRTest.java b/src/test/java/com/android/tools/r8/naming/AvoidRTest.java
new file mode 100644
index 0000000..4633b36
--- /dev/null
+++ b/src/test/java/com/android/tools/r8/naming/AvoidRTest.java
@@ -0,0 +1,144 @@
+// Copyright (c) 2019, the R8 project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+package com.android.tools.r8.naming;
+
+import static com.android.tools.r8.utils.DescriptorUtils.getSimpleClassNameFromDescriptor;
+import static com.android.tools.r8.utils.codeinspector.Matchers.isRenamed;
+import static org.junit.Assert.assertNotEquals;
+import static org.junit.Assert.assertThat;
+import static org.junit.Assert.assertTrue;
+
+import com.android.tools.r8.R8TestBuilder;
+import com.android.tools.r8.jasmin.JasminBuilder;
+import com.android.tools.r8.jasmin.JasminTestBase;
+import com.android.tools.r8.utils.FileUtils;
+import com.android.tools.r8.utils.StringUtils;
+import com.google.common.collect.ImmutableSet;
+import java.nio.file.Path;
+import java.util.HashSet;
+import java.util.Set;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.Parameterized;
+import org.junit.runners.Parameterized.Parameters;
+
+@RunWith(Parameterized.class)
+public class AvoidRTest extends JasminTestBase {
+  private Backend backend;
+
+  @Parameters(name = "Backend: {0}")
+  public static Backend[] data() {
+    return Backend.values();
+  }
+
+  public AvoidRTest(Backend backend) {
+    this.backend = backend;
+  }
+
+  @Test
+  public void test_withObfuscationDictionary() throws Exception {
+    Path dictionary = temp.newFile("dictionary.txt").toPath();
+    FileUtils.writeTextFile(dictionary, StringUtils.lines("P", "Q", "R", "S", "T"));
+    Set<String> expectedNames = ImmutableSet.of("P", "Q", "S", "T");
+
+    JasminBuilder jasminBuilder = new JasminBuilder();
+    R8TestBuilder builder = testForR8(backend);
+    for (int i = 0; i < 4; i++) {
+      jasminBuilder.addClass("TopLevel" + Integer.toString(i));
+    }
+    for (int i = 0; i < 4; i++) {
+      jasminBuilder.addClass("p1/SecondLevel" + Integer.toString(i));
+    }
+    for (int i = 0; i < 4; i++) {
+      jasminBuilder.addClass("p1/p2/ThirdLevel" + Integer.toString(i));
+    }
+    for (int i = 0; i < 4; i++) {
+      jasminBuilder.addClass("p2/SecondLevel" + Integer.toString(i));
+    }
+    builder.addProgramClassFileData(jasminBuilder.buildClasses());
+    Set<String> usedDescriptors = new HashSet<>();
+    builder.noTreeShaking()
+        .addKeepRules("-classobfuscationdictionary " + dictionary)
+        .compile()
+        .inspect(codeInspector -> {
+          codeInspector.forAllClasses(classSubject -> {
+            assertThat(classSubject, isRenamed());
+            String renamedDescriptor = classSubject.getFinalDescriptor();
+            assertTrue(usedDescriptors.add(renamedDescriptor));
+            assertNotEquals("R", getSimpleClassNameFromDescriptor(renamedDescriptor));
+            assertTrue(expectedNames.contains(getSimpleClassNameFromDescriptor(renamedDescriptor)));
+          });
+        });
+  }
+
+  @Test
+  public void test_withoutPackageHierarchy() throws Exception {
+    JasminBuilder jasminBuilder = new JasminBuilder();
+    R8TestBuilder builder = testForR8(backend);
+    for (int i = 0; i < 26 * 2; i++) {
+      jasminBuilder.addClass("TestClass" + Integer.toString(i));
+    }
+    builder.addProgramClassFileData(jasminBuilder.buildClasses());
+    Set<String> usedNames = new HashSet<>();
+    builder.noTreeShaking()
+        .compile()
+        .inspect(codeInspector -> {
+          codeInspector.forAllClasses(classSubject -> {
+            assertThat(classSubject, isRenamed());
+            assertTrue(usedNames.add(classSubject.getFinalName()));
+            assertNotEquals("R", classSubject.getFinalName());
+          });
+        });
+    assertTrue(usedNames.contains("Q"));
+    assertTrue(usedNames.contains("S"));
+  }
+
+  private void test_withPackageHierarchy(String keepRule) throws Exception {
+    R8TestBuilder builder = testForR8(backend);
+    JasminBuilder jasminBuilder = new JasminBuilder();
+    for (int i = 0; i < 26 * 2; i++) {
+      jasminBuilder.addClass("TopLevel" + Integer.toString(i));
+    }
+    for (int i = 0; i < 26 * 2; i++) {
+      jasminBuilder.addClass("p1/SecondLevel" + Integer.toString(i));
+    }
+    for (int i = 0; i < 26 * 2; i++) {
+      jasminBuilder.addClass("p1/p2/ThirdLevel" + Integer.toString(i));
+    }
+    for (int i = 0; i < 26 * 2; i++) {
+      jasminBuilder.addClass("p2/SecondLevel" + Integer.toString(i));
+    }
+    builder.addProgramClassFileData(jasminBuilder.buildClasses());
+    Set<String> usedDescriptors = new HashSet<>();
+    builder.noTreeShaking()
+        .addKeepRules(keepRule)
+        .compile()
+        .inspect(codeInspector -> {
+          codeInspector.forAllClasses(classSubject -> {
+            assertThat(classSubject, isRenamed());
+            String renamedDescriptor = classSubject.getFinalDescriptor();
+            assertTrue(usedDescriptors.add(renamedDescriptor));
+            assertNotEquals("R", getSimpleClassNameFromDescriptor(renamedDescriptor));
+          });
+        });
+  }
+
+  @Test
+  public void test_withPackageHierarchy_default() throws Exception {
+    test_withPackageHierarchy("");
+  }
+
+  @Test
+  public void test_withPackageHierarchy_repackage() throws Exception {
+    // Repackage every class to the top-level.
+    test_withPackageHierarchy("-repackageclasses");
+  }
+
+  @Test
+  public void test_withPackageHierarchy_flatten() throws Exception {
+    // Repackage every package to the top-level.
+    test_withPackageHierarchy("-flattenpackagehierarchy");
+  }
+
+}