diff --git a/pkg/compiler/lib/src/js_emitter/startup_emitter/model_emitter.dart b/pkg/compiler/lib/src/js_emitter/startup_emitter/model_emitter.dart
index d660d94..4495763 100644
--- a/pkg/compiler/lib/src/js_emitter/startup_emitter/model_emitter.dart
+++ b/pkg/compiler/lib/src/js_emitter/startup_emitter/model_emitter.dart
@@ -352,17 +352,15 @@
 
   /// Generates a simple header that provides the compiler's build id.
   js.Comment buildGeneratedBy() {
-    StringBuffer flavor = new StringBuffer();
-    flavor.write('fast startup emitter');
-    // TODO(johnniwinther): Remove this flavor.
-    flavor.write(', strong');
+    final flavor = StringBuffer();
+    flavor.write(_options.nullSafetyMode);
     if (_options.trustPrimitives) flavor.write(', trust primitives');
     if (_options.omitImplicitChecks) flavor.write(', omit checks');
     if (_options.laxRuntimeTypeToString) {
       flavor.write(', lax runtime type');
     }
     if (_options.useContentSecurityPolicy) flavor.write(', CSP');
-    return new js.Comment(generatedBy(_options, flavor: '$flavor'));
+    return js.Comment(generatedBy(_options, flavor: '$flavor'));
   }
 
   js.Statement buildDeferredInitializerGlobal() {