diff --git a/pkg/front_end/lib/src/api_unstable/bazel_worker.dart b/pkg/front_end/lib/src/api_unstable/bazel_worker.dart
index 95ca894e164..66f4a23a1be 100644
--- a/pkg/front_end/lib/src/api_unstable/bazel_worker.dart
+++ b/pkg/front_end/lib/src/api_unstable/bazel_worker.dart
@@ -25,6 +25,8 @@ import '../api_prototype/file_system.dart' show FileSystem;
 
 import '../api_prototype/front_end.dart' show CompilerResult;
 
+import '../base/nnbd_mode.dart' show NnbdMode;
+
 import '../base/processed_options.dart' show ProcessedOptions;
 
 import '../kernel_generator_impl.dart' show generateKernel;
@@ -50,6 +52,8 @@ export '../api_prototype/standard_file_system.dart' show StandardFileSystem;
 export '../api_prototype/terminal_color_support.dart'
     show printDiagnosticMessage;
 
+export '../base/nnbd_mode.dart' show NnbdMode;
+
 export '../fasta/kernel/utils.dart' show serializeComponent;
 
 export 'compiler_state.dart' show InitializedCompilerState;
@@ -72,7 +76,8 @@ Future<InitializedCompilerState> initializeIncrementalCompiler(
     bool outlineOnly,
     Map<String, String> environmentDefines,
     {bool trackNeededDillLibraries: false,
-    bool verbose: false}) async {
+    bool verbose: false,
+    NnbdMode nnbdMode: NnbdMode.Weak}) async {
   List<Component> outputLoadedAdditionalDills =
       new List<Component>(additionalDills.length);
   Map<ExperimentalFlag, bool> experimentalFlags = parseExperimentalFlags(
@@ -94,7 +99,8 @@ Future<InitializedCompilerState> initializeIncrementalCompiler(
       omitPlatform: true,
       trackNeededDillLibraries: trackNeededDillLibraries,
       environmentDefines: environmentDefines,
-      verbose: verbose);
+      verbose: verbose,
+      nnbdMode: nnbdMode);
 }
 
 Future<InitializedCompilerState> initializeCompiler(
@@ -108,6 +114,7 @@ Future<InitializedCompilerState> initializeCompiler(
   Iterable<String> experiments,
   Map<String, String> environmentDefines, {
   bool verbose: false,
+  NnbdMode nnbdMode: NnbdMode.Weak,
 }) async {
   // TODO(sigmund): use incremental compiler when it supports our use case.
   // Note: it is common for the summary worker to invoke the compiler with the
@@ -125,7 +132,8 @@ Future<InitializedCompilerState> initializeCompiler(
     ..experimentalFlags = parseExperimentalFlags(
         parseExperimentalArguments(experiments),
         onError: (e) => throw e)
-    ..verbose = verbose;
+    ..verbose = verbose
+    ..nnbdMode = nnbdMode;
 
   ProcessedOptions processedOpts = new ProcessedOptions(options: options);
 
diff --git a/utils/bazel/kernel_worker.dart b/utils/bazel/kernel_worker.dart
index 779ec623c4d..194fe5527a0 100644
--- a/utils/bazel/kernel_worker.dart
+++ b/utils/bazel/kernel_worker.dart
@@ -144,7 +144,8 @@ final summaryArgsParser = new ArgParser()
   ..addMultiOption('enable-experiment',
       help: 'Enable a language experiment when invoking the CFE.')
   ..addMultiOption('define', abbr: 'D')
-  ..addFlag('verbose', defaultsTo: false);
+  ..addFlag('verbose', defaultsTo: false)
+  ..addFlag('sound-null-safety', defaultsTo: false);
 
 class ComputeKernelResult {
   final bool succeeded;
@@ -187,6 +188,9 @@ Future<ComputeKernelResult> computeKernel(List<String> args,
   var sources = (parsedArgs['source'] as List<String>).map(_toUri).toList();
   var excludeNonSources = parsedArgs['exclude-non-sources'] as bool;
 
+  var nnbdMode = parsedArgs['sound-null-safety'] as bool
+      ? fe.NnbdMode.Strong
+      : fe.NnbdMode.Weak;
   var summaryOnly = parsedArgs['summary-only'] as bool;
   var trackWidgetCreation = parsedArgs['track-widget-creation'] as bool;
 
@@ -294,7 +298,8 @@ Future<ComputeKernelResult> computeKernel(List<String> args,
         summaryOnly,
         environmentDefines,
         trackNeededDillLibraries: recordUsedInputs,
-        verbose: verbose);
+        verbose: verbose,
+        nnbdMode: nnbdMode);
   } else {
     state = await fe.initializeCompiler(
         // TODO(sigmund): pass an old state once we can make use of it.
@@ -307,7 +312,8 @@ Future<ComputeKernelResult> computeKernel(List<String> args,
         fileSystem,
         parsedArgs['enable-experiment'] as List<String>,
         environmentDefines,
-        verbose: verbose);
+        verbose: verbose,
+        nnbdMode: nnbdMode);
   }
 
   void onDiagnostic(fe.DiagnosticMessage message) {