diff --git a/pkg/analysis_server/test/domain_edit_dartfix_test.dart b/pkg/analysis_server/test/domain_edit_dartfix_test.dart
index c4f13642d65..c1b942b2496 100644
--- a/pkg/analysis_server/test/domain_edit_dartfix_test.dart
+++ b/pkg/analysis_server/test/domain_edit_dartfix_test.dart
@@ -171,17 +171,8 @@ void test() {
 }
 ''');
     createProject();
-    EditDartfixResult result =
-        await performFix(includedFixes: ['non-nullable']);
-    expect(result.suggestions.length, greaterThanOrEqualTo(1));
-    expect(result.hasErrors, isFalse);
-    expectEdits(result.edits, '''
-int f(int? i) => 0;
-int g(int? i) => f(i);
-void test() {
-  g(null);
-}
-''');
+    expectLater(() async => await performFix(includedFixes: ['non-nullable']),
+        throwsA(TypeMatcher<StateError>()));
   }
 
   Future<void> test_nonNullable_analysisOptions_created() async {
diff --git a/pkg/dartdev/test/commands/migrate_test.dart b/pkg/dartdev/test/commands/migrate_test.dart
index 513ddc33019..a3b0c7923bd 100644
--- a/pkg/dartdev/test/commands/migrate_test.dart
+++ b/pkg/dartdev/test/commands/migrate_test.dart
@@ -7,6 +7,10 @@ import 'package:test/test.dart';
 
 import '../utils.dart';
 
+// TODO(jcollins-g): Set to true and/or remove when when NNBD is enabled in the
+//  SDK running this test.
+bool _nnbdIsEnabled = false;
+
 void main() {
   group('migrate', defineMigrateTests);
 }
@@ -30,24 +34,34 @@ void defineMigrateTests() {
 
   test('directory implicit', () {
     p = project(mainSrc: 'int get foo => 1;\n');
-    var result =
-        p.runSync('migrate', ['--no-web-preview'], workingDir: p.dirPath);
-    expect(result.exitCode, 0);
-    expect(result.stderr, isEmpty);
+    var result = p.runSync(
+        'migrate',
+        [
+          '--no-web-preview',
+          '--server-path=${p.absolutePathToAnalysisServerFile}'
+        ],
+        workingDir: p.dirPath);
+    expect(result.exitCode, _nnbdIsEnabled ? 0 : 2);
+    expect(result.stderr, _nnbdIsEnabled ? isEmpty : isNotEmpty);
     expect(result.stdout, contains('Generating migration suggestions'));
   });
 
   test('directory explicit', () {
     p = project(mainSrc: 'int get foo => 1;\n');
-    var result = p.runSync('migrate', ['--no-web-preview', p.dirPath]);
-    expect(result.exitCode, 0);
-    expect(result.stderr, isEmpty);
+    var result = p.runSync('migrate', [
+      '--no-web-preview',
+      '--server-path=${p.absolutePathToAnalysisServerFile}',
+      p.dirPath
+    ]);
+    expect(result.exitCode, _nnbdIsEnabled ? 0 : 2);
+    expect(result.stderr, _nnbdIsEnabled ? isEmpty : isNotEmpty);
     expect(result.stdout, contains('Generating migration suggestions'));
   });
 
   test('bad directory', () {
     p = project(mainSrc: 'int get foo => 1;\n');
-    var result = p.runSync('migrate', ['foo_bar_dir']);
+    var result = p.runSync('migrate',
+        ['--server-path=${p.absolutePathToAnalysisServerFile}', 'foo_bar_dir']);
     expect(result.exitCode, 64);
     expect(result.stderr,
         contains('not found; please provide a path to a package or directory'));
diff --git a/pkg/dartdev/test/utils.dart b/pkg/dartdev/test/utils.dart
index f852731cda1..2a354eaa915 100644
--- a/pkg/dartdev/test/utils.dart
+++ b/pkg/dartdev/test/utils.dart
@@ -63,18 +63,34 @@ class TestProject {
     );
   }
 
-  /// The path relative from `Directory.current.path` to `dartdev.dart` is
-  /// different when executing these tests locally versus on the Dart
-  /// buildbots, this if-else captures this change and branches for each case.
-  String get absolutePathToDartdevFile {
-    var dartdevFilePathOnBots = path.absolute(path.join(
-        Directory.current.path, 'pkg', 'dartdev', 'bin', 'dartdev.dart'));
-    if (File(dartdevFilePathOnBots).existsSync()) {
-      return dartdevFilePathOnBots;
-    } else {
-      return path
-          .absolute(path.join(Directory.current.path, 'bin', 'dartdev.dart'));
+  String _sdkRootPath;
+
+  /// Return the root of the SDK.
+  String get sdkRootPath {
+    if (_sdkRootPath == null) {
+      // Assumes the script importing this one is somewhere under the SDK.
+      String current = path.canonicalize(Platform.script.toFilePath());
+      do {
+        String tryDir = path.dirname(current);
+        if (File(path.join(tryDir, 'pkg', 'dartdev', 'bin', 'dartdev.dart'))
+            .existsSync()) {
+          _sdkRootPath = tryDir;
+          return _sdkRootPath;
+        }
+        current = tryDir;
+      } while (path.dirname(current) != current);
+      throw StateError('can not find SDK repository root');
     }
+    return _sdkRootPath;
+  }
+
+  String get absolutePathToDartdevFile {
+    return path.join(sdkRootPath, 'pkg', 'dartdev', 'bin', 'dartdev.dart');
+  }
+
+  String get absolutePathToAnalysisServerFile {
+    return path.join(
+        sdkRootPath, 'pkg', 'analysis_server', 'bin', 'server.dart');
   }
 
   File findFile(String name) {
diff --git a/pkg/dartfix/lib/src/migrate/migrate.dart b/pkg/dartfix/lib/src/migrate/migrate.dart
index 621a03e5468..f8339949ecb 100644
--- a/pkg/dartfix/lib/src/migrate/migrate.dart
+++ b/pkg/dartfix/lib/src/migrate/migrate.dart
@@ -12,6 +12,7 @@ import 'package:analysis_server_client/server.dart';
 import 'package:args/command_runner.dart';
 import 'package:cli_util/cli_logging.dart';
 import 'package:path/path.dart' as path;
+import 'package:nnbd_migration/src/messages.dart';
 
 import '../util.dart';
 import 'apply.dart';
@@ -430,6 +431,18 @@ class _ServerNotifications with NotificationHandler {
   void onAnalysisErrors(AnalysisErrorsParams event) {
     _analysisErrorsController.add(event);
   }
+
+  @override
+  void onServerError(ServerErrorParams event) {
+    stderr.writeln('encountered error: ${event.message}');
+
+    for (String fatal in [migratedAlready, nnbdExperimentOff, sdkNnbdOff]) {
+      if (event.message.contains(fatal)) {
+        server.kill();
+        exit(2);
+      }
+    }
+  }
 }
 
 class _ServerListener with ServerListener {
diff --git a/pkg/nnbd_migration/lib/src/messages.dart b/pkg/nnbd_migration/lib/src/messages.dart
new file mode 100644
index 00000000000..3a32d14f076
--- /dev/null
+++ b/pkg/nnbd_migration/lib/src/messages.dart
@@ -0,0 +1,9 @@
+// Copyright (c) 2020, the Dart project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+const String migratedAlready =
+    "Seem to be migrating code that's already migrated";
+const String nnbdExperimentOff =
+    'Analyzer seems to need the nnbd experiment on in the SDK.';
+const String sdkNnbdOff = 'Analysis seems to have an SDK without NNBD enabled.';
diff --git a/pkg/nnbd_migration/lib/src/nullability_migration_impl.dart b/pkg/nnbd_migration/lib/src/nullability_migration_impl.dart
index 0dda2f2fddd..48d2fbcce9d 100644
--- a/pkg/nnbd_migration/lib/src/nullability_migration_impl.dart
+++ b/pkg/nnbd_migration/lib/src/nullability_migration_impl.dart
@@ -3,6 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 import 'package:analysis_server/src/protocol_server.dart';
+import 'package:analyzer/dart/analysis/features.dart';
 import 'package:analyzer/dart/analysis/results.dart';
 import 'package:analyzer/file_system/physical_file_system.dart';
 import 'package:analyzer/src/generated/resolver.dart';
@@ -15,6 +16,7 @@ import 'package:nnbd_migration/src/edge_builder.dart';
 import 'package:nnbd_migration/src/edit_plan.dart';
 import 'package:nnbd_migration/src/fix_aggregator.dart';
 import 'package:nnbd_migration/src/fix_builder.dart';
+import 'package:nnbd_migration/src/messages.dart';
 import 'package:nnbd_migration/src/node_builder.dart';
 import 'package:nnbd_migration/src/nullability_node.dart';
 import 'package:nnbd_migration/src/postmortem_file.dart';
@@ -79,6 +81,7 @@ class NullabilityMigrationImpl implements NullabilityMigration {
 
   @override
   void finalizeInput(ResolvedUnitResult result) {
+    _sanityCheck(result);
     if (!_propagated) {
       _propagated = true;
       _graph.propagate(_postmortemFileWriter);
@@ -127,6 +130,7 @@ class NullabilityMigrationImpl implements NullabilityMigration {
   }
 
   void prepareInput(ResolvedUnitResult result) {
+    _sanityCheck(result);
     if (_variables == null) {
       _variables = Variables(_graph, result.typeProvider,
           instrumentation: _instrumentation,
@@ -145,6 +149,7 @@ class NullabilityMigrationImpl implements NullabilityMigration {
   }
 
   void processInput(ResolvedUnitResult result) {
+    _sanityCheck(result);
     var unit = result.unit;
     try {
       DecoratedTypeParameterBounds.current = _decoratedTypeParameterBounds;
@@ -167,6 +172,26 @@ class NullabilityMigrationImpl implements NullabilityMigration {
     _graph.update(_postmortemFileWriter);
   }
 
+  void _sanityCheck(ResolvedUnitResult result) {
+    final equalsParamType = result.typeProvider.objectType
+        .getMethod('==')
+        .parameters[0]
+        .type
+        .getDisplayString(withNullability: true);
+    if (equalsParamType == 'Object*') {
+      throw StateError(nnbdExperimentOff);
+    }
+
+    if (equalsParamType != 'Object') {
+      throw StateError(sdkNnbdOff);
+    }
+
+    if (result.unit.featureSet.isEnabled(Feature.non_nullable)) {
+      // TODO(jcollins-g): Allow for skipping already migrated compilation units.
+      throw StateError('$migratedAlready: ${result.path}');
+    }
+  }
+
   static Location _computeLocation(
       LineInfo lineInfo, SourceEdit edit, Source source) {
     final locationInfo = lineInfo.getLocation(edit.offset);