diff --git a/sdk/lib/io/process.dart b/sdk/lib/io/process.dart
index 8ceb41d9e7d..1c9fddb985e 100644
--- a/sdk/lib/io/process.dart
+++ b/sdk/lib/io/process.dart
@@ -46,7 +46,11 @@ set exitCode(int status) {
  * in a isolate while it is blocked in a [sleep] call.
  */
 void sleep(Duration duration) {
-  _ProcessUtils._sleep(duration.inMilliseconds);
+  int milliseconds = duration.inMilliseconds;
+  if (milliseconds < 0) {
+    throw new ArgumentError("sleep: duration cannot be negative");
+  }
+  _ProcessUtils._sleep(milliseconds);
 }
 
 /**
diff --git a/tests/standalone/io/sleep_test.dart b/tests/standalone/io/sleep_test.dart
index d953bf9f1a2..26646fa87a6 100644
--- a/tests/standalone/io/sleep_test.dart
+++ b/tests/standalone/io/sleep_test.dart
@@ -13,7 +13,10 @@ test(int milliseconds) {
 }
 
 main() {
+  test(0);
   test(1);
   test(10);
   test(100);
+  Expect.throws(() => sleep(new Duration(milliseconds: -1)),
+                (e) => e is ArgumentError);
 }