diff --git a/packages/flutter_tools/lib/src/test/coverage_collector.dart b/packages/flutter_tools/lib/src/test/coverage_collector.dart
index cd28f52b2b..3c553b53aa 100644
--- a/packages/flutter_tools/lib/src/test/coverage_collector.dart
+++ b/packages/flutter_tools/lib/src/test/coverage_collector.dart
@@ -15,6 +15,7 @@ class CoverageCollector {
   static final CoverageCollector instance = new CoverageCollector();
 
   bool enabled = false;
+  int observatoryPort;
 
   void collectCoverage({
     String host,
diff --git a/packages/flutter_tools/lib/src/test/flutter_platform.dart b/packages/flutter_tools/lib/src/test/flutter_platform.dart
index 58a6a82508..4e3f114ab8 100644
--- a/packages/flutter_tools/lib/src/test/flutter_platform.dart
+++ b/packages/flutter_tools/lib/src/test/flutter_platform.dart
@@ -114,7 +114,7 @@ void main() {
 
     int observatoryPort;
     if (CoverageCollector.instance.enabled) {
-      observatoryPort = new math.Random().nextInt(30000) + 2000;
+      observatoryPort = CoverageCollector.instance.observatoryPort ?? new math.Random().nextInt(30000) + 2000;
       await CoverageCollector.instance.finishPendingJobs();
     }