diff --git a/packages/flutter_tools/lib/src/build_system/targets/web.dart b/packages/flutter_tools/lib/src/build_system/targets/web.dart
index 52281b8477..e7dd430a73 100644
--- a/packages/flutter_tools/lib/src/build_system/targets/web.dart
+++ b/packages/flutter_tools/lib/src/build_system/targets/web.dart
@@ -137,10 +137,10 @@ class Dart2JSTarget extends Target {
       '--libraries-spec=$specPath',
       if (dart2jsOptimization != null)
         '-$dart2jsOptimization'
-      else if (buildMode == BuildMode.profile)
-        '-O1'
       else
         '-O4',
+      if (buildMode == BuildMode.profile)
+        '--no-minify',
       '-o',
       outputFile.path,
       '--packages=$packageFile',
diff --git a/packages/flutter_tools/test/general.shard/build_system/targets/web_test.dart b/packages/flutter_tools/test/general.shard/build_system/targets/web_test.dart
index a3a7fb963c..816ff559ea 100644
--- a/packages/flutter_tools/test/general.shard/build_system/targets/web_test.dart
+++ b/packages/flutter_tools/test/general.shard/build_system/targets/web_test.dart
@@ -158,7 +158,8 @@ void main() {
       fs.path.join('bin', 'cache', 'dart-sdk', 'bin', 'dart'),
       fs.path.join('bin', 'cache', 'dart-sdk', 'bin', 'snapshots', 'dart2js.dart.snapshot'),
       '--libraries-spec=' + fs.path.join('bin', 'cache', 'flutter_web_sdk', 'libraries.json'),
-      '-O1', // lowest optimizations.
+      '-O4', // highest optimizations
+      '--no-minify', // but uses unminified names for debugging
       '-o',
       environment.buildDir.childFile('main.dart.js').absolute.path,
       '--packages=.packages',