diff --git a/src/main/java/com/android/tools/r8/ir/optimize/CodeRewriter.java b/src/main/java/com/android/tools/r8/ir/optimize/CodeRewriter.java
index 30244bf..02c06da 100644
--- a/src/main/java/com/android/tools/r8/ir/optimize/CodeRewriter.java
+++ b/src/main/java/com/android/tools/r8/ir/optimize/CodeRewriter.java
@@ -1651,7 +1651,7 @@
           && outValue.isUsed()
           && outValue.numberOfPhiUsers() == 0
           && outValue.uniqueUsers().stream().allMatch(isCheckcastToSubtype)) {
-        removeOrReplaceByDebugLocalWrite(it, inValue, outValue);
+        removeOrReplaceByDebugLocalWrite(checkCast, it, inValue, outValue);
         continue;
       }
 
@@ -1671,7 +1671,7 @@
         if (TypeLatticeElement.lessThanOrEqual(appInfo, inTypeLattice, castTypeLattice)) {
           assert outTypeLattice.equals(inTypeLattice);
           needToRemoveTrivialPhis = needToRemoveTrivialPhis || outValue.numberOfPhiUsers() != 0;
-          removeOrReplaceByDebugLocalWrite(it, inValue, outValue);
+          removeOrReplaceByDebugLocalWrite(checkCast, it, inValue, outValue);
           continue;
         }
         // Otherwise, keep the checkcast to preserve verification errors. E.g., down-cast:
@@ -1691,16 +1691,20 @@
     if (needToRemoveTrivialPhis) {
       code.removeAllTrivialPhis();
     }
-    it = code.instructionIterator();
     assert code.isConsistentSSA();
   }
 
   private void removeOrReplaceByDebugLocalWrite(
-      InstructionIterator it, Value inValue, Value outValue) {
-    if (outValue.getLocalInfo() != inValue.getLocalInfo() && outValue.hasLocalInfo()) {
+      Instruction currentInstruction, InstructionIterator it, Value inValue, Value outValue) {
+    if (outValue.hasLocalInfo() && outValue.getLocalInfo() != inValue.getLocalInfo()) {
       DebugLocalWrite debugLocalWrite = new DebugLocalWrite(outValue, inValue);
       it.replaceCurrentInstruction(debugLocalWrite);
     } else {
+      if (outValue.hasLocalInfo()) {
+        assert outValue.getLocalInfo() == inValue.getLocalInfo();
+        // Should remove the end-marker before replacing the current instruction.
+        currentInstruction.removeDebugValue(outValue.getLocalInfo());
+      }
       outValue.replaceUsers(inValue);
       it.removeOrReplaceByDebugLocalRead();
     }
diff --git a/src/test/java/com/android/tools/r8/TestBase.java b/src/test/java/com/android/tools/r8/TestBase.java
index 403ee70..fa35d0d 100644
--- a/src/test/java/com/android/tools/r8/TestBase.java
+++ b/src/test/java/com/android/tools/r8/TestBase.java
@@ -12,8 +12,11 @@
 import com.android.tools.r8.ToolHelper.ArtCommandBuilder;
 import com.android.tools.r8.ToolHelper.DexVm;
 import com.android.tools.r8.ToolHelper.ProcessResult;
+import com.android.tools.r8.cf.code.CfInstruction;
 import com.android.tools.r8.code.Instruction;
 import com.android.tools.r8.errors.Unreachable;
+import com.android.tools.r8.graph.CfCode;
+import com.android.tools.r8.graph.Code;
 import com.android.tools.r8.graph.DexCode;
 import com.android.tools.r8.graph.DexEncodedMethod;
 import com.android.tools.r8.graph.SmaliWriter;
@@ -827,6 +830,13 @@
         .map(kind::cast);
   }
 
+  protected Stream<CfInstruction> filterInstructionKind(
+      CfCode code, Class<? extends CfInstruction> kind) {
+    return code.getInstructions().stream()
+        .filter(kind::isInstance)
+        .map(kind::cast);
+  }
+
   public enum MinifyMode {
     NONE,
     JAVA,
diff --git a/src/test/java/com/android/tools/r8/debug/DebugTestBase.java b/src/test/java/com/android/tools/r8/debug/DebugTestBase.java
index 99222d0..b6cdb48 100644
--- a/src/test/java/com/android/tools/r8/debug/DebugTestBase.java
+++ b/src/test/java/com/android/tools/r8/debug/DebugTestBase.java
@@ -3,6 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 package com.android.tools.r8.debug;
 
+import com.android.tools.r8.TestBase;
 import com.android.tools.r8.ToolHelper;
 import com.android.tools.r8.ToolHelper.ArtCommandBuilder;
 import com.android.tools.r8.ToolHelper.DexVm;
@@ -79,7 +80,7 @@
  * The protocol messages are described here:
  * https://docs.oracle.com/javase/8/docs/platform/jpda/jdwp/jdwp-protocol.html
  */
-public abstract class DebugTestBase {
+public abstract class DebugTestBase extends TestBase {
 
   // Set to true to enable verbose logs
   private static final boolean DEBUG_TESTS = false;
diff --git a/src/test/java/com/android/tools/r8/ir/optimize/checkcast/CheckCastDebugTest.java b/src/test/java/com/android/tools/r8/ir/optimize/checkcast/CheckCastDebugTest.java
new file mode 100644
index 0000000..6d6b4c7
--- /dev/null
+++ b/src/test/java/com/android/tools/r8/ir/optimize/checkcast/CheckCastDebugTest.java
@@ -0,0 +1,55 @@
+// Copyright (c) 2018, 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.ir.optimize.checkcast;
+
+import com.android.tools.r8.NeverInline;
+
+class A {
+  @NeverInline
+  @Override
+  public String toString() {
+    return "A";
+  }
+}
+
+class B extends A {
+  @NeverInline
+  @Override
+  public String toString() {
+    return super.toString() + "B";
+  }
+}
+
+class C extends B {
+  @NeverInline
+  @Override
+  public String toString() {
+    return super.toString() + "C";
+  }
+}
+
+class CheckCastDebugTest {
+  @NeverInline
+  static void differentLocals() {
+    Object obj = new C();
+    A a = (A) obj;
+    B b = (B) a;
+    C c = (C) b;
+    System.out.println(c.toString());
+  }
+
+  @NeverInline
+  static void sameLocal() {
+    Object obj = new C();
+    obj = (A) obj;
+    obj = (B) obj;
+    obj = (C) obj;
+    System.out.println(obj.toString());
+  }
+
+  public static void main(String[] args) {
+    differentLocals();
+    sameLocal();
+  }
+}
diff --git a/src/test/java/com/android/tools/r8/ir/optimize/checkcast/CheckCastDebugTestRunner.java b/src/test/java/com/android/tools/r8/ir/optimize/checkcast/CheckCastDebugTestRunner.java
new file mode 100644
index 0000000..44720ed
--- /dev/null
+++ b/src/test/java/com/android/tools/r8/ir/optimize/checkcast/CheckCastDebugTestRunner.java
@@ -0,0 +1,178 @@
+// Copyright (c) 2018, 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.ir.optimize.checkcast;
+
+import static com.android.tools.r8.utils.codeinspector.Matchers.isPresent;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertThat;
+
+import com.android.tools.r8.ClassFileConsumer;
+import com.android.tools.r8.CompilationMode;
+import com.android.tools.r8.DexIndexedConsumer;
+import com.android.tools.r8.NeverInline;
+import com.android.tools.r8.R8Command;
+import com.android.tools.r8.ToolHelper;
+import com.android.tools.r8.cf.code.CfCheckCast;
+import com.android.tools.r8.debug.CfDebugTestConfig;
+import com.android.tools.r8.debug.DebugTestBase;
+import com.android.tools.r8.debug.DebugTestConfig;
+import com.android.tools.r8.debug.DexDebugTestConfig;
+import com.android.tools.r8.graph.Code;
+import com.android.tools.r8.code.CheckCast;
+import com.android.tools.r8.origin.Origin;
+import com.android.tools.r8.utils.AndroidApp;
+import com.android.tools.r8.utils.codeinspector.ClassSubject;
+import com.android.tools.r8.utils.codeinspector.CodeInspector;
+import com.android.tools.r8.utils.codeinspector.MethodSubject;
+import com.google.common.collect.ImmutableList;
+import java.nio.file.Path;
+import java.util.Arrays;
+import java.util.Collection;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.Parameterized;
+
+@RunWith(Parameterized.class)
+public class CheckCastDebugTestRunner extends DebugTestBase {
+  private static final Class<?> MAIN = CheckCastDebugTest.class;
+  private final Backend backend;
+
+  private Path r8Out;
+  private CodeInspector inspector;
+
+  @Parameterized.Parameters(name = "Backend: {0}")
+  public static Collection<Backend> data() {
+    return Arrays.asList(Backend.values());
+  }
+
+  public CheckCastDebugTestRunner(Backend backend) {
+    this.backend = backend;
+  }
+
+  private static int testCounter = 0;
+
+  @Before
+  public void setUp() throws Exception {
+    AndroidApp app = readClasses(NeverInline.class, A.class, B.class, C.class, MAIN);
+    r8Out = temp.newFile(String.format("r8Out-%s-%d.zip", backend, testCounter++)).toPath();
+    R8Command.Builder builder = ToolHelper.prepareR8CommandBuilder(app);
+    if (backend == Backend.DEX) {
+      builder.setProgramConsumer(new DexIndexedConsumer.ArchiveConsumer(r8Out));
+    } else {
+      assert backend == Backend.CF;
+      builder.setProgramConsumer(new ClassFileConsumer.ArchiveConsumer(r8Out));
+    }
+    builder.addProguardConfiguration(
+        ImmutableList.of(
+            "-dontobfuscate",
+            keepMainProguardConfigurationWithInliningAnnotation(MAIN)),
+        Origin.unknown());
+    builder.setMode(CompilationMode.DEBUG);
+    ToolHelper.allowTestProguardOptions(builder);
+    ToolHelper.runR8(builder.build(), o -> o.enableVerticalClassMerging = false);
+    inspector = new CodeInspector(r8Out);
+    ClassSubject classSubject = inspector.clazz(MAIN);
+    assertThat(classSubject, isPresent());
+  }
+
+  @Test
+  public void test_differentLocals() throws Throwable {
+    ClassSubject classSubject = inspector.clazz(MAIN);
+    MethodSubject method = classSubject.method("void", "differentLocals", ImmutableList.of());
+    assertThat(method, isPresent());
+    long count = countCheckCast(method.getMethod().getCode());
+    assertEquals(1, count);
+
+    DebugTestConfig config = backend == Backend.CF
+        ? new CfDebugTestConfig()
+        : new DexDebugTestConfig();
+    config.addPaths(r8Out);
+    runDebugTest(config, MAIN.getCanonicalName(),
+        // Object obj = new C();
+        breakpoint(MAIN.getCanonicalName(), "differentLocals", "()V", 35),
+        run(),
+        checkNoLocal("obj"),
+        checkNoLocal("a"),
+        checkNoLocal("b"),
+        checkNoLocal("c"),
+        // A a = (A) obj;
+        breakpoint(MAIN.getCanonicalName(), "differentLocals", "()V", 36),
+        run(),
+        checkLocal("obj"),
+        checkNoLocal("a"),
+        checkNoLocal("b"),
+        checkNoLocal("c"),
+        // B b = (B) a;
+        breakpoint(MAIN.getCanonicalName(), "differentLocals", "()V", 37),
+        run(),
+        checkLocal("obj"),
+        checkLocal("a"),
+        checkNoLocal("b"),
+        checkNoLocal("c"),
+        // C c = (C) b;
+        breakpoint(MAIN.getCanonicalName(), "differentLocals", "()V", 38),
+        run(),
+        checkLocal("obj"),
+        checkLocal("a"),
+        checkLocal("b"),
+        checkNoLocal("c"),
+        // System.out.println(c.toString());
+        breakpoint(MAIN.getCanonicalName(), "differentLocals", "()V", 39),
+        run(),
+        checkLocal("obj"),
+        checkLocal("a"),
+        checkLocal("b"),
+        checkLocal("c"),
+        run()
+    );
+  }
+
+  @Test
+  public void test_sameLocal() throws Throwable {
+    ClassSubject classSubject = inspector.clazz(MAIN);
+    MethodSubject method = classSubject.method("void", "sameLocal", ImmutableList.of());
+    assertThat(method, isPresent());
+    long count = countCheckCast(method.getMethod().getCode());
+    assertEquals(1, count);
+
+    DebugTestConfig config = backend == Backend.CF
+        ? new CfDebugTestConfig()
+        : new DexDebugTestConfig();
+    config.addPaths(r8Out);
+    runDebugTest(config, MAIN.getCanonicalName(),
+        // Object obj = new C();
+        breakpoint(MAIN.getCanonicalName(), "sameLocal", "()V", 44),
+        run(),
+        checkNoLocal("obj"),
+        // obj = (A) obj;
+        breakpoint(MAIN.getCanonicalName(), "sameLocal", "()V", 45),
+        run(),
+        checkLocal("obj"),
+        // obj = (B) obj;
+        breakpoint(MAIN.getCanonicalName(), "sameLocal", "()V", 46),
+        run(),
+        checkLocal("obj"),
+        // obj = (C) obj;
+        breakpoint(MAIN.getCanonicalName(), "sameLocal", "()V", 47),
+        run(),
+        checkLocal("obj"),
+        // System.out.println(obj.toString());
+        breakpoint(MAIN.getCanonicalName(), "sameLocal", "()V", 48),
+        run(),
+        checkLocal("obj"),
+        run()
+    );
+  }
+
+  private long countCheckCast(Code code) {
+    if (backend == Backend.DEX) {
+      return filterInstructionKind(code.asDexCode(), CheckCast.class).count();
+    } else {
+      assert backend == Backend.CF;
+      return filterInstructionKind(code.asCfCode(), CfCheckCast.class).count();
+    }
+  }
+
+}
diff --git a/src/test/java/com/android/tools/r8/ir/optimize/checkcast/CheckCastRemovalTest.java b/src/test/java/com/android/tools/r8/ir/optimize/checkcast/CheckCastRemovalTest.java
index b141955..c953515 100644
--- a/src/test/java/com/android/tools/r8/ir/optimize/checkcast/CheckCastRemovalTest.java
+++ b/src/test/java/com/android/tools/r8/ir/optimize/checkcast/CheckCastRemovalTest.java
@@ -99,7 +99,7 @@
   }
 
   @Test
-  public void downCasts() throws Exception {
+  public void downCasts_noLocal() throws Exception {
     JasminBuilder builder = new JasminBuilder();
     // C < B < A
     ClassBuilder a = builder.addClass("A");
@@ -133,6 +133,91 @@
   }
 
   @Test
+  public void downCasts_differentLocals() throws Exception {
+    JasminBuilder builder = new JasminBuilder();
+    // C < B < A
+    ClassBuilder a = builder.addClass("A");
+    a.addDefaultConstructor();
+    ClassBuilder b = builder.addClass("B", "A");
+    b.addDefaultConstructor();
+    ClassBuilder c = builder.addClass("C", "B");
+    c.addDefaultConstructor();
+    ClassBuilder classBuilder = builder.addClass(CLASS_NAME);
+    MethodSignature main = classBuilder.addMainMethod(
+        ".limit stack 3",
+        ".limit locals 3",
+        ".var 0 is a LA; from Label1 to Label2",
+        ".var 1 is b LB; from Label1 to Label2",
+        ".var 2 is c LC; from Label1 to Label2",
+        "Label1:",
+        "new A",
+        "dup",
+        "invokespecial A/<init>()V",
+        "astore_0",
+        "aload_0",
+        "checkcast B", // Gone
+        "astore_1",
+        "aload_1",
+        "checkcast C", // Should be kept to preserve cast exception
+        "astore_2",
+        "Label2:",
+        "return");
+
+    List<String> pgConfigs = ImmutableList.of(
+        "-keep class " + CLASS_NAME + " { *; }",
+        "-keep class A { *; }",
+        "-keep class B { *; }",
+        "-keep class C { *; }",
+        "-dontoptimize",
+        "-dontshrink");
+    AndroidApp app = compileWithR8InDebugMode(builder, pgConfigs, null, backend);
+
+    checkCheckCasts(app, main, "C");
+    checkRuntimeException(builder, app, CLASS_NAME, "ClassCastException");
+  }
+
+  @Test
+  public void downCasts_sameLocal() throws Exception {
+    JasminBuilder builder = new JasminBuilder();
+    // C < B < A
+    ClassBuilder a = builder.addClass("A");
+    a.addDefaultConstructor();
+    ClassBuilder b = builder.addClass("B", "A");
+    b.addDefaultConstructor();
+    ClassBuilder c = builder.addClass("C", "B");
+    c.addDefaultConstructor();
+    ClassBuilder classBuilder = builder.addClass(CLASS_NAME);
+    MethodSignature main = classBuilder.addMainMethod(
+        ".limit stack 3",
+        ".limit locals 1",
+        ".var 0 is a LA; from Label1 to Label2",
+        "Label1:",
+        "new A",
+        "dup",
+        "invokespecial A/<init>()V",
+        "astore_0",
+        "aload_0",
+        "checkcast B", // Gone
+        "astore_0",
+        "aload_0",
+        "checkcast C", // Should be kept to preserve cast exception
+        "Label2:",
+        "return");
+
+    List<String> pgConfigs = ImmutableList.of(
+        "-keep class " + CLASS_NAME + " { *; }",
+        "-keep class A { *; }",
+        "-keep class B { *; }",
+        "-keep class C { *; }",
+        "-dontoptimize",
+        "-dontshrink");
+    AndroidApp app = compileWithR8InDebugMode(builder, pgConfigs, null, backend);
+
+    checkCheckCasts(app, main, "C");
+    checkRuntimeException(builder, app, CLASS_NAME, "ClassCastException");
+  }
+
+  @Test
   public void bothUpAndDowncast() throws Exception {
     JasminBuilder builder = new JasminBuilder();
     ClassBuilder classBuilder = builder.addClass(CLASS_NAME);
@@ -180,7 +265,7 @@
         "-dontshrink");
     AndroidApp app = compileWithR8(builder, pgConfigs, null, backend);
 
-    checkCheckCasts(app, main, "Example");
+    checkCheckCasts(app, main, null);
     checkRuntimeException(builder, app, CLASS_NAME, "NullPointerException");
   }
 
@@ -201,6 +286,7 @@
       assertTrue(!found && instruction.isCheckCast(maybeType));
       found = true;
     }
+    assertTrue(found);
   }
 
   private void checkRuntime(JasminBuilder builder, AndroidApp app, String className)
diff --git a/src/test/java/com/android/tools/r8/jasmin/JasminTestBase.java b/src/test/java/com/android/tools/r8/jasmin/JasminTestBase.java
index f106793..cfc49fe 100644
--- a/src/test/java/com/android/tools/r8/jasmin/JasminTestBase.java
+++ b/src/test/java/com/android/tools/r8/jasmin/JasminTestBase.java
@@ -5,6 +5,7 @@
 
 import static org.junit.Assert.fail;
 
+import com.android.tools.r8.CompilationMode;
 import com.android.tools.r8.OutputMode;
 import com.android.tools.r8.R8Command;
 import com.android.tools.r8.TestBase;
@@ -106,6 +107,21 @@
     return ToolHelper.runR8(builder.build(), optionsConsumer);
   }
 
+  protected AndroidApp compileWithR8InDebugMode(
+      JasminBuilder builder,
+      List<String> proguardConfigs,
+      Consumer<InternalOptions> optionsConsumer,
+      Backend backend)
+      throws Exception {
+    R8Command command =
+        ToolHelper.prepareR8CommandBuilder(builder.build(), emptyConsumer(backend))
+            .addLibraryFiles(runtimeJar(backend))
+            .addProguardConfiguration(proguardConfigs, Origin.unknown())
+            .setMode(CompilationMode.DEBUG)
+            .build();
+    return ToolHelper.runR8(command, optionsConsumer);
+  }
+
   protected AndroidApp compileWithR8(
       JasminBuilder builder,
       List<String> proguardConfigs,