diff --git a/lib/isolate/isolate_leg.dart b/lib/isolate/isolate_leg.dart
index a80e7fd8ffc..d953b9ad0af 100644
--- a/lib/isolate/isolate_leg.dart
+++ b/lib/isolate/isolate_leg.dart
@@ -47,7 +47,7 @@
  * Called by the compiler to support switching
  * between isolates when we get a callback from the DOM.
  */
-void _callInIsolate(IsolateContext isolate, Function function) {
+void _callInIsolate(_IsolateContext isolate, Function function) {
   isolate.eval(function);
   _globalState.topEventLoop.run();
 }