diff --git a/src/main/java/com/android/tools/r8/ir/desugar/DesugaredLibraryAPIConverter.java b/src/main/java/com/android/tools/r8/ir/desugar/DesugaredLibraryAPIConverter.java
index d45a68c..2393956 100644
--- a/src/main/java/com/android/tools/r8/ir/desugar/DesugaredLibraryAPIConverter.java
+++ b/src/main/java/com/android/tools/r8/ir/desugar/DesugaredLibraryAPIConverter.java
@@ -273,22 +273,22 @@
     appView.options().reporter.warning(new StringDiagnostic(sb.toString()));
   }
 
-  private void warnInvalidInvoke(DexType type, DexMethod invokedMethod, String debugString) {
+  public void reportInvalidInvoke(DexType type, DexMethod invokedMethod, String debugString) {
     DexType desugaredType = appView.rewritePrefix.rewrittenType(type);
     appView
         .options()
         .reporter
-        .warning(
+        .info(
             new StringDiagnostic(
                 "Invoke to "
                     + invokedMethod.holder
                     + "#"
                     + invokedMethod.name
-                    + " may not work correctly at runtime ("
+                    + " may not work correctly at runtime (Cannot convert "
                     + debugString
-                    + " type "
+                    + "type "
                     + desugaredType
-                    + " is a desugared type)."));
+                    + ")."));
   }
 
   public static DexType vivifiedTypeFor(DexType type, AppView<?> appView) {
@@ -306,6 +306,7 @@
       InstructionListIterator iterator,
       ListIterator<BasicBlock> blockIterator) {
     DexMethod invokedMethod = invokeMethod.getInvokedMethod();
+    boolean invalidConversion = false;
     if (trackedAPIs != null) {
       trackedAPIs.add(invokedMethod);
     }
@@ -320,12 +321,13 @@
         // Return conversion added only if return value is used.
         if (invokeMethod.outValue() != null
             && invokeMethod.outValue().numberOfUsers() + invokeMethod.outValue().numberOfPhiUsers()
-            > 0) {
+                > 0) {
           returnConversion =
               createReturnConversionAndReplaceUses(code, invokeMethod, returnType, newReturnType);
         }
       } else {
-        warnInvalidInvoke(returnType, invokeMethod.getInvokedMethod(), "return");
+        reportInvalidInvoke(returnType, invokeMethod.getInvokedMethod(), "return ");
+        invalidConversion = true;
         newReturnType = returnType;
       }
     } else {
@@ -353,7 +355,8 @@
               createParameterConversion(code, argType, argVivifiedType, inValue));
           newInValues.add(parameterConversions.get(parameterConversions.size() - 1).outValue());
         } else {
-          warnInvalidInvoke(argType, invokeMethod.getInvokedMethod(), "parameter");
+          reportInvalidInvoke(argType, invokeMethod.getInvokedMethod(), "parameter ");
+          invalidConversion = true;
           newInValues.add(invokeMethod.inValues().get(i + receiverShift));
         }
       } else {
@@ -373,7 +376,8 @@
             invokeMethod.outValue(),
             newInValues);
     assert newDexMethod
-        == methodWithVivifiedTypeInSignature(invokedMethod, invokedMethod.holder, appView);
+            == methodWithVivifiedTypeInSignature(invokedMethod, invokedMethod.holder, appView)
+        || invalidConversion;
 
     // Insert and reschedule all instructions.
     iterator.previous();
diff --git a/src/main/java/com/android/tools/r8/ir/desugar/DesugaredLibraryWrapperSynthesizer.java b/src/main/java/com/android/tools/r8/ir/desugar/DesugaredLibraryWrapperSynthesizer.java
index 99994fe..ed86a23 100644
--- a/src/main/java/com/android/tools/r8/ir/desugar/DesugaredLibraryWrapperSynthesizer.java
+++ b/src/main/java/com/android/tools/r8/ir/desugar/DesugaredLibraryWrapperSynthesizer.java
@@ -125,7 +125,7 @@
 
   boolean canGenerateWrapper(DexType type) {
     DexClass dexClass = appView.definitionFor(type);
-    if (dexClass == null) {
+    if (dexClass == null || dexClass.accessFlags.isFinal()) {
       return false;
     }
     return dexClass.isLibraryClass() || appView.options().isDesugaredLibraryCompilation();
@@ -162,18 +162,9 @@
   private DexClass getValidClassToWrap(DexType type) {
     DexClass dexClass = appView.definitionFor(type);
     // The dexClass should be a library class, so it cannot be null.
-    assert dexClass != null
-        && (dexClass.isLibraryClass() || appView.options().isDesugaredLibraryCompilation());
-    if (dexClass.accessFlags.isFinal()) {
-      throw appView
-          .options()
-          .reporter
-          .fatalError(
-              new StringDiagnostic(
-                  "Cannot generate a wrapper for final class "
-                      + dexClass.type
-                      + ". Add a custom conversion in the desugared library."));
-    }
+    assert dexClass != null;
+    assert dexClass.isLibraryClass() || appView.options().isDesugaredLibraryCompilation();
+    assert !dexClass.accessFlags.isFinal();
     return dexClass;
   }
 
diff --git a/src/main/java/com/android/tools/r8/ir/synthetic/DesugaredLibraryAPIConversionCfCodeProvider.java b/src/main/java/com/android/tools/r8/ir/synthetic/DesugaredLibraryAPIConversionCfCodeProvider.java
index 5597bb5..3cb579f 100644
--- a/src/main/java/com/android/tools/r8/ir/synthetic/DesugaredLibraryAPIConversionCfCodeProvider.java
+++ b/src/main/java/com/android/tools/r8/ir/synthetic/DesugaredLibraryAPIConversionCfCodeProvider.java
@@ -30,7 +30,6 @@
 import com.android.tools.r8.ir.code.If;
 import com.android.tools.r8.ir.code.ValueType;
 import com.android.tools.r8.ir.desugar.DesugaredLibraryAPIConverter;
-import com.android.tools.r8.utils.StringDiagnostic;
 import java.util.ArrayList;
 import java.util.List;
 import org.objectweb.asm.Opcodes;
@@ -41,24 +40,14 @@
     super(appView, holder);
   }
 
-  boolean shouldConvert(
-      DexType type, DesugaredLibraryAPIConverter converter, DexString methodName) {
+  boolean shouldConvert(DexType type, DesugaredLibraryAPIConverter converter, DexMethod method) {
     if (!appView.rewritePrefix.hasRewrittenType(type)) {
       return false;
     }
     if (converter.canConvert(type)) {
       return true;
     }
-    appView
-        .options()
-        .reporter
-        .warning(
-            new StringDiagnostic(
-                "Desugared library API conversion failed for "
-                    + type
-                    + ", unexpected behavior for method "
-                    + methodName
-                    + "."));
+    converter.reportInvalidInvoke(type, method, "");
     return false;
   }
 
@@ -101,7 +90,7 @@
       DexType[] newParameters = forwardMethod.proto.parameters.values.clone();
       for (DexType param : forwardMethod.proto.parameters.values) {
         instructions.add(new CfLoad(ValueType.fromDexType(param), stackIndex));
-        if (shouldConvert(param, converter, forwardMethod.name)) {
+        if (shouldConvert(param, converter, forwardMethod)) {
           instructions.add(
               new CfInvoke(
                   Opcodes.INVOKESTATIC,
@@ -132,7 +121,7 @@
         instructions.add(new CfInvoke(Opcodes.INVOKEVIRTUAL, newForwardMethod, false));
       }
 
-      if (shouldConvert(returnType, converter, forwardMethod.name)) {
+      if (shouldConvert(returnType, converter, forwardMethod)) {
         instructions.add(
             new CfInvoke(
                 Opcodes.INVOKESTATIC,
@@ -188,7 +177,7 @@
       int stackIndex = 1;
       for (DexType param : forwardMethod.proto.parameters.values) {
         instructions.add(new CfLoad(ValueType.fromDexType(param), stackIndex));
-        if (shouldConvert(param, converter, forwardMethod.name)) {
+        if (shouldConvert(param, converter, forwardMethod)) {
           instructions.add(
               new CfInvoke(
                   Opcodes.INVOKESTATIC,
@@ -208,7 +197,7 @@
       }
 
       DexType returnType = forwardMethod.proto.returnType;
-      if (shouldConvert(returnType, converter, forwardMethod.name)) {
+      if (shouldConvert(returnType, converter, forwardMethod)) {
         instructions.add(
             new CfInvoke(
                 Opcodes.INVOKESTATIC,
diff --git a/src/test/java/com/android/tools/r8/desugar/desugaredlibrary/conversiontests/APIConversionFinalClassErrorTest.java b/src/test/java/com/android/tools/r8/desugar/desugaredlibrary/conversiontests/APIConversionFinalClassErrorTest.java
deleted file mode 100644
index 403ae3c..0000000
--- a/src/test/java/com/android/tools/r8/desugar/desugaredlibrary/conversiontests/APIConversionFinalClassErrorTest.java
+++ /dev/null
@@ -1,57 +0,0 @@
-// 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.desugar.desugaredlibrary.conversiontests;
-
-import static junit.framework.TestCase.assertEquals;
-import static junit.framework.TestCase.fail;
-
-import com.android.tools.r8.CompilationFailedException;
-import com.android.tools.r8.TestDiagnosticMessages;
-import com.android.tools.r8.desugar.desugaredlibrary.DesugaredLibraryTestBase;
-import com.android.tools.r8.utils.AndroidApiLevel;
-import java.time.Year;
-import org.junit.Test;
-
-public class APIConversionFinalClassErrorTest extends DesugaredLibraryTestBase {
-
-  @Test
-  public void testFinalMethod() {
-    try {
-      testForD8()
-          .setMinApi(AndroidApiLevel.B)
-          .addProgramClasses(Executor.class)
-          .addLibraryClasses(CustomLibClass.class)
-          .enableCoreLibraryDesugaring(AndroidApiLevel.B)
-          .compileWithExpectedDiagnostics(this::assertDiagnosis);
-      fail("Expected compilation error");
-    } catch (CompilationFailedException ignored) {
-
-    }
-  }
-
-  private void assertDiagnosis(TestDiagnosticMessages d) {
-    assertEquals(
-        "Cannot generate a wrapper for final class java.time.Year."
-            + " Add a custom conversion in the desugared library.",
-        d.getErrors().get(0).getDiagnosticMessage());
-  }
-
-  static class Executor {
-
-    public static void main(String[] args) {
-      System.out.println(CustomLibClass.call(Year.now()));
-    }
-  }
-
-  // This class will be put at compilation time as library and on the runtime class path.
-  // This class is convenient for easy testing. Each method plays the role of methods in the
-  // platform APIs for which argument/return values need conversion.
-  static class CustomLibClass {
-
-    public static long call(Year year) {
-      return 0L;
-    }
-  }
-}
diff --git a/src/test/java/com/android/tools/r8/desugar/desugaredlibrary/conversiontests/APIConversionFinalClassTest.java b/src/test/java/com/android/tools/r8/desugar/desugaredlibrary/conversiontests/APIConversionFinalClassTest.java
new file mode 100644
index 0000000..0c13b40
--- /dev/null
+++ b/src/test/java/com/android/tools/r8/desugar/desugaredlibrary/conversiontests/APIConversionFinalClassTest.java
@@ -0,0 +1,89 @@
+// 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.desugar.desugaredlibrary.conversiontests;
+
+import static org.hamcrest.core.StringContains.containsString;
+
+import com.android.tools.r8.TestParameters;
+import com.android.tools.r8.ToolHelper;
+import com.android.tools.r8.desugar.desugaredlibrary.DesugaredLibraryTestBase;
+import com.android.tools.r8.utils.AndroidApiLevel;
+import com.android.tools.r8.utils.BooleanUtils;
+import java.nio.file.Path;
+import java.time.Year;
+import java.util.List;
+import org.junit.BeforeClass;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.Parameterized;
+
+@RunWith(Parameterized.class)
+public class APIConversionFinalClassTest extends DesugaredLibraryTestBase {
+
+  private final TestParameters parameters;
+  private final boolean shrinkDesugaredLibrary;
+
+  private static final AndroidApiLevel MIN_SUPPORTED = AndroidApiLevel.O;
+
+  private static Path customLib;
+
+  @Parameterized.Parameters(name = "{0}, shrinkDesugaredLibrary: {1}")
+  public static List<Object[]> data() {
+    return buildParameters(getTestParameters().withDexRuntimesStartingFromIncluding(ToolHelper.DexVm.Version.V7_0_0).withApiLevelsEndingAtIncluding(AndroidApiLevel.M).build(), BooleanUtils.values());
+  }
+
+  public APIConversionFinalClassTest(TestParameters parameters, boolean shrinkDesugaredLibrary) {
+    this.shrinkDesugaredLibrary = shrinkDesugaredLibrary;
+    this.parameters = parameters;
+  }
+
+  @BeforeClass
+  public static void compileCustomLib() throws Exception {
+    customLib =
+        testForD8(getStaticTemp())
+            .addProgramClasses(CustomLibClass.class)
+            .setMinApi(MIN_SUPPORTED)
+            .compile()
+            .writeToZip();
+  }
+
+  @Test
+  public void testFinalMethod() throws Exception {
+    KeepRuleConsumer keepRuleConsumer = createKeepRuleConsumer(parameters);
+    testForD8()
+        .setMinApi(AndroidApiLevel.B)
+        .addProgramClasses(Executor.class)
+        .addLibraryClasses(CustomLibClass.class)
+        .enableCoreLibraryDesugaring(parameters.getApiLevel(), keepRuleConsumer)
+        .compile()
+        .addDesugaredCoreLibraryRunClassPath(
+            this::buildDesugaredLibrary,
+            parameters.getApiLevel(),
+            keepRuleConsumer.get(),
+            shrinkDesugaredLibrary)
+        .addRunClasspathFiles(customLib)
+        .run(parameters.getRuntime(), Executor.class)
+        .assertFailureWithErrorThatMatches(containsString("NoSuchMethodError"));
+  }
+
+  static class Executor {
+
+    public static void main(String[] args) {
+      System.out.println(CustomLibClass.libCall(Year.now()));
+    }
+  }
+
+  // This class will be put at compilation time as library and on the runtime class path.
+  // This class is convenient for easy testing. Each method plays the role of methods in the
+  // platform APIs for which argument/return values need conversion.
+  static class CustomLibClass {
+
+    // We use Year because Year is a final class with no custom conversion but Year has been
+    // unused in the Android library so far.
+    public static long libCall(Year year) {
+      return 0L;
+    }
+  }
+}