diff --git a/web_sdk/BUILD.gn b/web_sdk/BUILD.gn
index 142f6606496d6..68e4634ed4190 100644
--- a/web_sdk/BUILD.gn
+++ b/web_sdk/BUILD.gn
@@ -165,7 +165,7 @@ prebuilt_dart_action("flutter_dartdevc_kernel_sdk") {
     "dart:_engine",
     "--no-summarize",
     "--packages",
-    "file:///" + rebase_path("//third_party/dart/.packages"),
+    "file://" + rebase_path("//third_party/dart/.packages"),
     "--multi-root-scheme",
     "org-dartlang-sdk",
     "--multi-root",
@@ -173,7 +173,8 @@ prebuilt_dart_action("flutter_dartdevc_kernel_sdk") {
     "--multi-root-output-path",
     rebase_path("$root_out_dir/"),
     "--libraries-file",
-    "file:///" + rebase_path("$root_out_dir/flutter_web_sdk/libraries.json"),
+    "file://" + rebase_path("$root_out_dir/flutter_web_sdk/libraries.json"),
+    "--inline-source-map",
     "--modules",
     "amd",
     "-o",