diff --git a/src/main/java/com/android/tools/r8/BaseCompilerCommand.java b/src/main/java/com/android/tools/r8/BaseCompilerCommand.java
index 5f65f6a..9dc1cc9 100644
--- a/src/main/java/com/android/tools/r8/BaseCompilerCommand.java
+++ b/src/main/java/com/android/tools/r8/BaseCompilerCommand.java
@@ -540,6 +540,16 @@
         }
         reporter.error(builder.toString());
       }
+      if (getMinApiLevel() > AndroidApiLevel.LATEST.getLevel()) {
+        if (getMinApiLevel() != AndroidApiLevel.magicApiLevelUsedByAndroidPlatformBuild) {
+          reporter.warning(
+              "An API level of "
+                  + getMinApiLevel()
+                  + " is not supported by this compiler. Please use an API level of "
+                  + AndroidApiLevel.LATEST.getLevel()
+                  + " or earlier");
+        }
+      }
       super.validate();
     }
   }
diff --git a/src/main/java/com/android/tools/r8/ir/desugar/BackportedMethodRewriter.java b/src/main/java/com/android/tools/r8/ir/desugar/BackportedMethodRewriter.java
index acdad7d..1d9c597 100644
--- a/src/main/java/com/android/tools/r8/ir/desugar/BackportedMethodRewriter.java
+++ b/src/main/java/com/android/tools/r8/ir/desugar/BackportedMethodRewriter.java
@@ -70,6 +70,7 @@
   private final IRConverter converter;
   private final DexItemFactory factory;
   private final RewritableMethods rewritableMethods;
+  private final boolean enable;
 
   private final Set<DexType> holders = Sets.newConcurrentHashSet();
   private final Map<DexMethod, MethodProvider> methodProviders = new ConcurrentHashMap<>();
@@ -79,6 +80,13 @@
     this.converter = converter;
     this.factory = appView.dexItemFactory();
     this.rewritableMethods = new RewritableMethods(appView.options(), appView);
+    // Disable rewriting if there are no methods to rewrite or if the API level is higher than
+    // the highest known API level when the compiler is built. This ensures that when this is used
+    // by the Android Platform build (which normally use an API level of 10000) there will be
+    // no rewriting of backported methods. See b/147480264.
+    this.enable =
+        !this.rewritableMethods.isEmpty()
+            && appView.options().minApiLevel <= AndroidApiLevel.LATEST.getLevel();
   }
 
   public static List<DexMethod> generateListOfBackportedMethods(AndroidApiLevel apiLevel) {
@@ -93,7 +101,7 @@
   }
 
   public void desugar(IRCode code) {
-    if (rewritableMethods.isEmpty()) {
+    if (!enable) {
       return; // Nothing to do!
     }
 
diff --git a/src/main/java/com/android/tools/r8/utils/AndroidApiLevel.java b/src/main/java/com/android/tools/r8/utils/AndroidApiLevel.java
index 1a21ffd..8c5c3b2 100644
--- a/src/main/java/com/android/tools/r8/utils/AndroidApiLevel.java
+++ b/src/main/java/com/android/tools/r8/utils/AndroidApiLevel.java
@@ -45,6 +45,8 @@
 
   public static final AndroidApiLevel LATEST = Q;
 
+  public static final int magicApiLevelUsedByAndroidPlatformBuild = 10000;
+
   private final int level;
 
   AndroidApiLevel(int level) {
diff --git a/src/main/java/com/android/tools/r8/utils/Reporter.java b/src/main/java/com/android/tools/r8/utils/Reporter.java
index 2541f47..ef17f80 100644
--- a/src/main/java/com/android/tools/r8/utils/Reporter.java
+++ b/src/main/java/com/android/tools/r8/utils/Reporter.java
@@ -38,6 +38,10 @@
     clientHandler.warning(warning);
   }
 
+  public void warning(String message) {
+    warning(new StringDiagnostic(message));
+  }
+
   @Override
   public synchronized void error(Diagnostic error) {
     clientHandler.error(error);
diff --git a/src/test/java/com/android/tools/r8/TestCompilerBuilder.java b/src/test/java/com/android/tools/r8/TestCompilerBuilder.java
index cc8d46a..dbad10b 100644
--- a/src/test/java/com/android/tools/r8/TestCompilerBuilder.java
+++ b/src/test/java/com/android/tools/r8/TestCompilerBuilder.java
@@ -78,6 +78,8 @@
     builder.setProgramConsumer(sink.wrapProgramConsumer(programConsumer));
     builder.setMainDexListConsumer(mainDexListConsumer);
     if (backend == Backend.DEX && defaultMinApiLevel != null) {
+      assert builder.getMinApiLevel() == 0
+          : "Don't set the API level directly through BaseCompilerCommand.Builder in tests";
       builder.setMinApiLevel(defaultMinApiLevel.getLevel());
     }
     if (useDefaultRuntimeLibrary) {
@@ -168,6 +170,9 @@
   }
 
   public T setMinApi(AndroidApiLevel minApiLevel) {
+    assert builder.getMinApiLevel() > 0 || this.defaultMinApiLevel != null
+        : "Tests must use this method to set min API level, and not"
+            + " BaseCompilerCommand.Builder.setMinApiLevel()";
     if (backend == Backend.DEX) {
       this.defaultMinApiLevel = null;
       builder.setMinApiLevel(minApiLevel.getLevel());
@@ -175,6 +180,14 @@
     return self();
   }
 
+  public T setMinApi(int minApiLevel) {
+    if (backend == Backend.DEX) {
+      this.defaultMinApiLevel = null;
+      builder.setMinApiLevel(minApiLevel);
+    }
+    return self();
+  }
+
   /** @deprecated use {@link #setMinApi(AndroidApiLevel)} instead. */
   @Deprecated
   public T setMinApi(TestRuntime runtime) {
diff --git a/src/test/java/com/android/tools/r8/desugar/backports/NoBackportForAndroidPlatform.java b/src/test/java/com/android/tools/r8/desugar/backports/NoBackportForAndroidPlatform.java
new file mode 100644
index 0000000..47081ab
--- /dev/null
+++ b/src/test/java/com/android/tools/r8/desugar/backports/NoBackportForAndroidPlatform.java
@@ -0,0 +1,128 @@
+// Copyright (c) 2020, 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.backports;
+
+import static org.hamcrest.core.StringContains.containsString;
+
+import com.android.tools.r8.TestBase;
+import com.android.tools.r8.TestParameters;
+import com.android.tools.r8.TestParametersCollection;
+import com.android.tools.r8.utils.AndroidApiLevel;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.Parameterized;
+import org.objectweb.asm.ClassWriter;
+import org.objectweb.asm.Label;
+import org.objectweb.asm.MethodVisitor;
+import org.objectweb.asm.Opcodes;
+
+@RunWith(Parameterized.class)
+public class NoBackportForAndroidPlatform extends TestBase implements Opcodes {
+
+  private final TestParameters parameters;
+
+  @Parameterized.Parameters(name = "{0}")
+  public static TestParametersCollection data() {
+    // The use of high API level will produce dex files with high DEX version, so only run on high
+    // API level VMs.
+    return getTestParameters()
+        .withDexRuntimes()
+        .withApiLevelsStartingAtIncluding(AndroidApiLevel.P)
+        .build();
+  }
+
+  public NoBackportForAndroidPlatform(TestParameters parameters) {
+    this.parameters = parameters;
+  }
+
+  @Test
+  public void backportSucceedsOnSupportedApiLevel() throws Exception {
+    testForD8()
+        .addProgramClassFileData(mainWithMathMultiplyExactLongInt())
+        .setMinApi(AndroidApiLevel.B)
+        .run(parameters.getRuntime(), "Test")
+        .assertSuccessWithOutputLines("4");
+  }
+
+  @Test
+  public void warningForNonPlatformBuild() throws Exception {
+    testForD8()
+        .addProgramClassFileData(mainWithMathMultiplyExactLongInt())
+        .setMinApi(30)
+        .compile()
+        .assertOnlyWarnings()
+        .assertWarningMessageThatMatches(
+            containsString("An API level of 30 is not supported by this compiler"))
+        .run(parameters.getRuntime(), "Test")
+        .assertFailureWithErrorThatMatches(
+            containsString("java.lang.NoSuchMethodError: No static method multiplyExact(JI)J"));
+  }
+
+  @Test
+  public void noWarningForPlatformBuild() throws Exception {
+    testForD8()
+        .addProgramClassFileData(mainWithMathMultiplyExactLongInt())
+        .setMinApi(AndroidApiLevel.magicApiLevelUsedByAndroidPlatformBuild)
+        .run(parameters.getRuntime(), "Test")
+        .assertFailureWithErrorThatMatches(
+            containsString("java.lang.NoSuchMethodError: No static method multiplyExact(JI)J"));
+  }
+
+  // Code for:
+  //
+  // class Test {
+  //   public static void main(String[] args) {
+  //     // Call Math.multiplyExact(long, int), which is not in Android Q.
+  //     System.out.println(Math.multiplyExact(2L, 2));
+  //   }
+  // }
+  //
+  private byte[] mainWithMathMultiplyExactLongInt() {
+
+    ClassWriter classWriter = new ClassWriter(0);
+    MethodVisitor methodVisitor;
+
+    classWriter.visit(V1_8, ACC_SUPER, "Test", null, "java/lang/Object", null);
+
+    classWriter.visitSource("Test.java", null);
+
+    {
+      methodVisitor = classWriter.visitMethod(0, "<init>", "()V", null, null);
+      methodVisitor.visitCode();
+      Label label0 = new Label();
+      methodVisitor.visitLabel(label0);
+      methodVisitor.visitLineNumber(1, label0);
+      methodVisitor.visitVarInsn(ALOAD, 0);
+      methodVisitor.visitMethodInsn(INVOKESPECIAL, "java/lang/Object", "<init>", "()V", false);
+      methodVisitor.visitInsn(RETURN);
+      methodVisitor.visitMaxs(1, 1);
+      methodVisitor.visitEnd();
+    }
+    {
+      methodVisitor =
+          classWriter.visitMethod(
+              ACC_PUBLIC | ACC_STATIC, "main", "([Ljava/lang/String;)V", null, null);
+      methodVisitor.visitCode();
+      Label label0 = new Label();
+      methodVisitor.visitLabel(label0);
+      methodVisitor.visitLineNumber(3, label0);
+      methodVisitor.visitFieldInsn(GETSTATIC, "java/lang/System", "out", "Ljava/io/PrintStream;");
+      methodVisitor.visitLdcInsn(Long.valueOf(2L));
+      methodVisitor.visitLdcInsn(Integer.valueOf(2));
+      methodVisitor.visitMethodInsn(
+          INVOKESTATIC, "java/lang/Math", "multiplyExact", "(JI)J", false);
+      methodVisitor.visitMethodInsn(INVOKEVIRTUAL, "java/io/PrintStream", "println", "(J)V", false);
+      Label label1 = new Label();
+      methodVisitor.visitLabel(label1);
+      methodVisitor.visitLineNumber(4, label1);
+      methodVisitor.visitInsn(RETURN);
+      methodVisitor.visitMaxs(5, 1);
+      methodVisitor.visitEnd();
+    }
+    classWriter.visitEnd();
+
+    return classWriter.toByteArray();
+  }
+}